Being able to join chat rooms from the Android app would be a plus! It would truly make us connected on the go, instead of having to sit down at our desks and open a browser window. This will allow more users to fully utilize the chat system and join events no matter where they are.
This is possible, but very far down the roadmap -- definitely not in v1 of any of the mobile apps. It'd be a pretty big change for both chat and the app, and chat activity just doesn't seem to be large enough to justify it yet (I know, a bit of a chicken-and-egg problem).
In the meantime, the web version is actually pretty good and we use it internally a fair amount.
Update Jan 2016: This is still something we'd like to do some day, but it's not on the roadmap after 2 years, so pretty unlikely.