I'm personally a big fan of roulette and slots and I look for casinos that allow me to use relatively small bet sizes (around 0.001 BTC).
If there's a progressive jackpot, that's also a big plus for me, especially if they don't require huge bets to be able to win it.
So let me hear what you are looking for in online Bitcoin casino's...
I look for if other players are playing there. Are high rollers playing? If it is a casino that has been around for at least a year and has many players, it will be a good experience. All of the casinos have the same games.