Slack has been a pretty decent solution for our team
We've used a slew of different messaging products over the years, but so far Slack has been a much better platform than the others.
The feature set is quite extensive and the UI is relatively well-suited to collaboration. We also have hooks going and coming from various other tools like PagerDuty and Service Now. The extensibility is not bad either. The options for formatting code as well as the thread-feature are essential options for me that are missing in some of the competing products.
There certainly are some shortcomings. Just to name a few:
- images are not optimized / reduced
- it's not possible to add people to an existing ad-hoc group chat
- search is counter-intuitive
My company uses both Hangouts and Slack at the moment, but the latter is by far my favorite.