Agree with you. It really is the wild west. Slowly the cream is rising to the top. I don't really bet that much anymore and the only place I play is Nitrogen because there lines are so good. Most I would trust them with is 1BTC or about $350. You can withdraw every night or even after every bet if you wanted. That's the nice part is you don't have to keep and trust so much money with a bitcoin book other then what you are currently betting.
The other huge disadvantage is the price volatility. It's hard enough to make any money doing this let alone having to battle the price of a bitcoin falling. Eventually is should stabilize but it will take a REALLY long time for that.
If those things are a concern it still is a great vehicle for getting money onto and off of standard books like 5D's and Heritage. You can go Bank account -> Circle.com -> 5Dimes and back the other way in about a half hour without leaving your computer or using a credit card. At the bare minimum it's great for that.