There has been lots of people complaining about the lack of screen space when trying to BMM their friends. The main reason is because that pesky action bar above the keyboard. To turn it off you just need to tap on the 3 dots on the bottom right, go to settings, then turn off the “show action bar with keyboard”. This doesn’t mean you can’t ever access the action bar. To get the action bar after you’ve turned it off, simply just tap on the chat portion of the BBM window and the keyboard goes away showing the action bar.
This essentially is how it works on BBM for BlackBerry’s. So I don’t really understand why you’d want the action bar even there all the time.