I can list off a few issues, but as usual, who and how many will share these experiences is a complete toss-up:
- random chunks of chat log can go temporarily missing at random when you scroll up. temporarily as in, they'll load on another device. on the regular one though, who knows when you'll get them back...
- if you manage to call someone the same time they do you, all bets are off. got things softlocked more than a few times.
- the usual recent Microsoft obsession with (keyboard-focus hijacking!) popups is of course also a thing in Teams
- text styling is hell, and sometimes when you click on the copy button in code blocks or copy out stuff in general, you get html tags polluting your copied data
- chats & group chats vs. team chats is extremely unnecessary and cumbersome
- multitenant support does a complete ui reload after which you miss notifications from the tenant you switched away from (might be different now)
- the localization is funky, just like in all other Microsoft products; from the small, like calendars starting on the wrong day, to the bigger, where if you ping @everyone in your Teams set to your native locale, then on the other side people will also see the ping in your native locale. It's just like Exchange/Outlook in this regard.
- the audio settings like getting mixed up, especially if you happen to disconnect and reconnect your stuff on the regular.
- they seemingly hardcode the URL preview thumbnail logic per trusted site, instead of using opengraph. their hardcoded integrations are also ignorant of e.g. url encoding and have other minor blemishes. I dare you to link the C++ wikipedia article to someone.
- profile pics go away sometimes (mine has been missing for weeks now, appears everywhere else), and statuses can get stuck or be null
These are all ongoing things that persist after years of use. Other, more questionable, already solved, or rare / one-off qualms would include:
- one time I tried screensharing, and when I clicked the button it showed me an emoji picker flyout instead of a share options flyout (lol)
- used to crash all the time in Edge of all things (not sure about other browsers), fixed since
- screenshare can freeze without you knowing any better thanks to the often extremely low framerate.
- slow (might be my terrible workstation)
- happily lies about delivery status and reorders messages