EDIT: Thank you all for detailing your experience with, and hatred for, this miserable product. Your display of solidarity is inspiring. Now, say it with me:
Came to Teams from Slack, some upsides, some downsides. It's a corporate communication tool, I don't use it because I think it's beautiful and elegant, I use it because I get paid money to use it.
I've had limited experience with slack, but the whole way conversations map to workspaces at least got to be confusing to me, and I would have liked an experience based on me as a user, rather than having my user span workspaces and have to juggle them to figure out how to talk to whoever I'm supposed to talk to at the time.