I haven't had the chance to play with real bitcoins yet, but I did with play money and I noticed a small bug: while the ball is spinning, it is possible to click on clear bets button. This increases your balance again, although once the ball is done spinning it gets corrected and you see the correct amount again.

Also I agree with Casascius's about the popup dialog: I think it would be better if it only shows when you click on an already placed bet. Although you already answered that point

For the rest, great job! I love the clean, minimalistic design of bitZino and the way roulette is implemented fits in nicely.