+1 for showcase. At first I thought it would be weird seeing lowercase letters on a keyboard but now it seems I make a lot less capitalization mistakes with it installed.
I'd like a 5 row keyboard but I've never tried one because none of them work in IOS 5 but I think the extra row might actually take up too much screen space.
I wouldn't mind a different color keyboard and some of the keyboards I've seen for ColorKeyboard look nice and all but it's not something I care enough about to spend money on.