Not working on slow internet connection
The Teams app and workflow is really great, but you constantly get slowed down or even knocked out when you're on a slow internet connection (even 450 Kbit/s is not enough).
Every couple of minutes, Teams shows "Please reconnect so we can keep your conversations going." even tough the connection is stable - but slow.
After some time, it suggests to reload the app, which takes ages. So it's not usable at all, which is very sad, considering how great it is.