I have been gambling on bitcoin for years now. The most stable and trustworthy one is unfortunately still primedice. Unfortunately because it means we lack innovation in bitcoin. I think I was expecting a lot more different gambling websites with a lot more competition but primedice still kicks ass comparing to most others.
Because of the irreversible and anonymous property of bitcoin, bitcoiners (including myself) in general consider trustworthiness to be an important factor, if not the most important factor, in choosing the site to play.
That's why the new sites couldn't create much competition IMO.