Teams, unlike pretty much every competing solution, is horrible when working with multiple different identities. If you have an account with an employer, a university and multiple clients, switching them is a pain (compare and contrast, for example, Slack). If you want to get a meeting in your Teams organization and invite a few people who are currently logged in their own organization, it is a pain to do so, and may involve them signing off of all kinds of other key MS tools they need to use during the meeting. If you want to use your phone to be in 'chats' of three different Teams organizations (e.g. three different consulting customers) at the same time, without switching between them but just monitoring all of them at the same time, I'm not sure if it can be reasonably done, and that IMHO is a relatively simple need and one which everyone else somehow manages to do better.

I have to use Google Hangouts or Meet or whatever it’s called now, Zoom, Teams and Slack Huddles. Teams consistently screws up audio, video or both! Then we end up back in Slack.

For the last couple of months, I occasionally don't get notifications if the app is not focused. And it's not just me, several team members are experiencing the same issue. Imagine-- a messaging app that doesn't deliver notifications when running in the background.

The UI is pretty awful in a bunch of ways. The performance is hit-or-miss at best. It's a resource hog. These are my top-line irritations with Teams. If I weren't forced to use it by my employer, I'd happily never touch it again.

The UI isn't smooth. Notifications will appear & then the message won't show up for a few seconds. Scrolling back through history can start flickering all over the place. It takes up a lot of memory

You running 64GB or 128Gb of ram?