well from an advertising class i took in school, it was taught that it is easier to read copy that is black on white, rather than inverted or outlined.
my vote would be for white, even though android chose to go inverted.
i must admit, it was tough to wrap my mind around it when i first started using it, because it seems like its missing something. but once you get the hang of it, it really does force you to zero in on the key you are trying to press. i'm liking it a lot.
i'm interested to see what kind of reception it gets before its further developed, but i have a couple thoughts....
1. add a black line along the top of the keyboard between it and the suggestion bar, same weight (thickness) as the letters. it'll make it look more finished.
2. it may help to expand (widen) the symbol for the spacebar... looks empty down there.
3. it would be cool to have some visual feedback like a water ripple or a glow around each letter as you hit it. i know that would probably take forever to do, but its fun to think big.