When you enable CURL it works nicely. (It should throw an error instead of "Server Error 500" when Session oder Curl doesn't work).
You can view Retweets, Replys and many other things and reply to them.
There is a "messages"-Feature, but since the plugin does not ask twitter for permissions to see the twitter-accounts private messages, there is nothing there.
I'm missing a key feature though: Send a new Tweet. There is no such entry or I didn't find it.