Microsoft Teams went generally available one week ago, on March 14, rolling out to Office 365 commercial tenants worldwide. We've been running it since the November preview, and this week the calls started: "We just finished deploying Skype for Business. Did we just buy a dead product?" It's a fair question — we operate a multi-tenant Skype for Business Server 2015 environment that carries 10,000-plus concurrent users at 99.95% availability, and we've built SfB estates for clients all through 2016. So the microsoft teams vs skype for business question is not academic for us. It's our own architecture on the table.
Short version, before the detail: no, your Skype for Business deployment is not dead, and anyone telling you to halt an in-flight SfB project because of last Tuesday is reacting to a press release rather than a product. But Teams is also not a toy, and the honest read of version one tells you a lot about where Microsoft is pointing the ship. Here's our read after four months of daily use and a week of GA.
A note on what GA actually shipped: Teams is now switched on by default for tenants (admins can manage it per-user via Office 365 licensing), it's included in Business Essentials, Business Premium, and the Enterprise E1/E3/E5 plans at no extra charge, and it launched across 181 markets in 19 languages. "Included in the license you already pay for" is the single most strategically interesting fact about it.
What Teams actually is at version one
Teams is persistent, channel-based group chat with the Office 365 stack bolted on properly. A team gets channels; channels get threaded conversations that persist forever, searchable, with @mentions, emoji, GIFs, and file sharing that lands in a SharePoint document library behind the scenes. Every team is an Office 365 Group under the hood, which means Exchange Online provides the calendar and mailbox plumbing, SharePoint Online provides files, and OneNote comes along for the ride. Tabs pin apps and documents to the top of a channel; connectors pipe in feeds from services like Twitter or a build system; there's a bot framework and T-Bot answering help questions with mixed success.
If that description sounds like Slack, that's because it is the Slack playbook — Microsoft is not being subtle. The difference is distribution and integration: Slack has to be bought, deployed, and integrated; Teams shows up inside the tenant you already own, pre-authenticated against Azure AD, pre-wired into the files and calendars your users already have. We watched this dynamic in the preview with our own consultants: nobody was told to use Teams, and within six weeks the internal email volume on project threads had visibly dropped. Persistent chat is genuinely better than reply-all for the fast-twitch coordination layer of a project. Skype for Business never had a good answer there — its Persistent Chat role exists, and in seven years we have met exactly two organizations that deployed it seriously.
The clients are solid for a v1: desktop apps for Windows and Mac, mobile apps for iOS, Android, and Windows Phone, and a capable web client. Calls and video between Teams users work and the quality is respectable — it's built on Skype infrastructure underneath.
Worth noting what four months of preview taught us about behavior, too. The teams that stuck with it were project-shaped: a defined group, a shared deliverable, a few months of intense coordination. The teams that went quiet were org-chart-shaped — "the whole department" teams created on day one out of enthusiasm, which produced thirty channels and no conversations. Channel design turned out to matter more than we expected: fewer channels, named after workstreams rather than topics, kept conversations findable. And search across persistent history is the sleeper feature — the third time someone retrieves a decision from a channel thread that would previously have died in someone's inbox, they stop using email for that kind of exchange entirely. None of this is in the datasheet, but it's what adoption actually hinges on.
What Teams is not — the v1 gap list
Now the other column, because this is where the "should we panic" question gets answered. As of GA, Teams has:
- No PSTN calling. No dial tone, no phone numbers, no Cloud PBX integration, no dial plans, no E911 story. Skype for Business — server or online — is Microsoft's only voice platform.
- No real meetings parity. Teams can do scheduled and ad-hoc meetings within a team, and they're fine for internal standups. But there's no anonymous external join experience worth the name, no dial-in conferencing (PSTN conferencing lives with SfB), no meeting room hardware ecosystem, no webinar-scale broadcast — Skype Meeting Broadcast handles the 10,000-viewer scenario.
- No guest access. You cannot invite anyone outside your tenant into a team. For consultancies, project teams with vendors, or anyone who works with clients — that's us, and probably you — this is the sharpest single limitation. Microsoft says external access is on the roadmap for later this year; today it's a wall.
- No federation. SfB federates with other organizations for presence and IM. Teams talks to your tenant and nothing else.
- Interop is thin. There's basic calling and IM interop plumbing between Teams and Skype for Business users, but presence doesn't unify cleanly and the experience depends on which client each side is sitting in. Plan for two islands, not a blend.
- Admin and compliance controls are young. Tenant-wide settings exist, per-user licensing controls exist, and the compliance fundamentals (the data lives in Office 365, so eDiscovery reaches the group mailbox and SharePoint content) are real. But policy granularity is nowhere near what Lync/SfB admins have with CsClientPolicy and friends, and there's no on-premises option at all — a hard stop for two of our government clients whose data cannot leave their environment.
Look at that list through an architect's eyes and the v1 positioning is obvious: Teams is the teamwork-chat layer, Skype for Business is the communications layer — voice, meetings, federation, external parties. Microsoft's own messaging at launch matches that split.
Why our SfB 2015 estates aren't dead
The multi-tenant Skype for Business platform we run exists because clients need PSTN voice, enterprise meetings, federation, regulated-industry deployment control, and contractually enforced availability — we engineer front-end pools, edge topology, and SIP domain isolation to hold 99.95% across 10,000-plus concurrent users because businesses run on that dial tone. Teams at GA addresses none of those requirements. Not "addresses them poorly" — does not address them.
That's the substance behind our advice this week: an in-flight Skype for Business Server 2015 deployment with a voice or meetings driver is still the right project in March 2017. Enterprise Voice migrations take 12 to 24 months at scale; whatever Teams becomes, organizations moving off legacy PBXs this year need a platform that terminates PSTN calls this year.
But we'd be lousy advisors if we ignored the signal in the noise. Microsoft made Teams the launch centerpiece, priced it into every Office 365 SKU, and built it cloud-only on the modern stack. The persistent-chat workload — the thing SfB never cracked — is now spoken for. When a vendor ships a new client that overlaps an old client's territory, history says the overlap grows in exactly one direction. We're not predicting dates; we're reading incentives. Our planning assumption is that Teams accumulates capabilities toward SfB Online over the next couple of years, and that on-premises SfB Server outlives SfB Online for the estates that need it. We'll revise when Microsoft says something concrete.
What we're telling clients to do this quarter
Concrete guidance, by situation:
| Your situation | Our advice this quarter |
|---|---|
| Mid-deployment on SfB Server 2015 (voice/meetings driver) | Finish it. The business case that justified it is untouched by Teams v1 |
| SfB Online for IM/presence only, no voice | Pilot Teams now with two or three real project teams — you may find chat adoption Teams-side is effortless where SfB IM adoption was pushed |
| Evaluating Slack | Run Teams in the bake-off. At marginal cost of zero against licenses you own, Slack now has to be better enough to justify a second identity and compliance boundary |
| Regulated / on-prem-only | No change. Teams has no on-premises story; SfB Server remains the platform |
| Everyone | Turn Teams on deliberately, not accidentally — it's enabled by default, so decide your governance posture (who can create teams, naming, the Office 365 Groups sprawl question) before your users decide it for you |
That last row deserves emphasis. Every team creates an Office 365 Group, a SharePoint site, and a shared mailbox. Tenants that never set Groups creation policy are about to discover Groups sprawl at Teams speed. Fifteen minutes with the AzureADPreview PowerShell module and a creation-restriction policy now saves an archaeology project later.
For the pilots specifically, we're prescriptive about shape: two or three real project teams, not a "Teams evaluation team" full of IT staff performing enthusiasm. Pick groups with a deliverable and a deadline, seed each team's channels for them on day one, and appoint one person per team who answers "where does this conversation go" questions for the first fortnight. Measure something honest at the end — email volume within the pilot group, or time-to-answer on internal questions — rather than logins, which measure curiosity, not adoption. And write down what you didn't deploy and why, because when guest access and meeting maturity land later this year, that document becomes your phase-two plan instead of a new debate.
And watch three specific things over the rest of 2017, because they're the tells: guest access (when consultants and vendors can join teams, adoption jumps a category), meeting maturity (dial-in and external join), and any statement putting Teams and SfB Online roadmaps in the same sentence. We'll be watching from inside both products — our own delivery teams now run project comms in Teams while our voice, meetings, and every client-facing call stay on the Skype for Business platform we maintain. That split is not indecision. At version one, it's the correct architecture.
If you're facing this
If you're mid-flight on Skype for Business and the launch coverage has your steering committee nervous, or you want a Teams pilot that doesn't turn into Groups sprawl, we've been running both products side by side since the preview and can show you what the coexistence actually looks like. Get in touch and we'll walk through your estate — dial tone, meetings, chat, and all — and put dates and dependencies on a one-page plan.