I really like this. My only issue is that I don't care for how light the message text is, on the white or dark backgrounds. In the dark versions, for example, it seems backwards to me that the screen names are bright white but the message text is a dull gray. It makes the message text hard to read, and that should be the *most* legible thing on the screen. I'd strongly suggest switching the emphasis: make the screen names a secondary color, like gray, and make the message text flat white or flat black, depending on the variation.