Just like Slack or Hipchat, Teams provides a seamless way to keep your staff in touch with each other, create groups (or teams if you will) to collaborate on specific problems, or really important matters such as organizing lunch.
It honestly feels like a beta. Being the SysAdmin here I get pretty frequent reports of things not working, with a few staff attempting to use Skype instead (this violates company policy, so that didn't last long, but it's a bad sign). Some pretty basic features (spellcheck, search) work if they feel like it, or sometimes not at all. MS does seem to be invested in making it work, you can track bugfixes and feature requests and so forth, and that's relatively neat.
Unfortunately many new features are implemented with the same apparent carelessness and are buggy or don't work properly (correcting messages is a cool feature, but it's terribly implemented, for example).
A few items to note:
Spellcheck works most of the time. Apparently at random it will flag correct items as incorrect for various users and will do so with the most random words until Teams is restarted. No Teams, "on" is not a typo.
A few users have Teams crash completely when accepting video calls, forcing their teams to use 3rd party video conferencing software, which is a huge issue. Per Microsoft this is a driver issue on the webcam. Replaced both the webcams with different models, as well as replaced the entire machine. Issue persists on those users. This only affects less than 2% of our staff, if more it would be a dealbreaker.
Teams constantly forces you to scroll down after new messages are received. Possibly the item that annoys me personally the most. Imagine an IM client, that will suddenly stop scrolling down automatically as new messages are incoming and you have to scroll down yourself. Two minutes later it does it again. Doesn't happen all the time, but enough to be frustrating.
The automatic status only seems to show activity in Teams occasionally. For example, someone who is busy working on a spreadsheet, Teams will occasionally show them as idle, since they are idle in TEAMS, even though they are not idle on their PC. This is happening a lot less now, so they possible started fixing this.
As of today (last day of 2017) I'd still treat this software as a beta. If you really like the available features and are willing to put up with some bugs and glitches (especially if you're willing to get involved in the community with bug reports and feature requests, which I have been) then go for it. Just realize there are MANY bugs, it's just a matter of if you'll encounter them or not. In another 6 to 12 months I feel this may mature enough that it should no longer be an issue.
The fancy buzzword "collaboration" I suppose. That's what most of the company is looking for, and this aspect actually worked out great for our engineering team (with caveats).
From the SysAdmin perspective we just need something that employees can use to stay in touch with each other, form specific groups they can chat with, be notified when mentioned, and from the admin perspective to manage these things relatively easily.
It does those things fine.
For the most part Teams does this quite well. Having previously using Pidgin with XMPP and then later Hipchat Business, I'd say Teams is working out better for us. I've never used Slack full time other than a trial, but it seems very comparable. It serves its purpose, and I think we'll stick with it. If the bugs get resolved, it does take care of all of our needs.