Were a team of 40 and we are using teams. It does work pretty well for most things, and I like all of the integration options. We had been using Mattermost prior to switching and a few of us still use that instead. The biggest issue I have with teams is the markdown support is not good. It tries to format as you type instead of letting you type markdown and have a type/preview mode. I've raised this on their forum and it doesn't appear to be anything they want to fix either. If they fixed that issue I wouldn't have any complaints.