I think the placement of the commit/undo/cancel buttons on the commit dialog seem a little out of place in relation to the comment window. This placement becomes a bit of a problem if the window is maximized (I run at 2048x1152, so the buttons are in the far bottom right corner of my screen.
My first commit via this dialog, it took me about 30 seconds to try and figure out how to actually "commit" because I couldn't find the buttons. My thought for best placement would be, above the diff view right below the commit message dialog since the message box and buttons are generally a pair.
If moving them isn't an option, could you please add some padding below them so they don't sit right on the bottom of the screen?