I've heard the key is to get into good clubs and that often they don't last so you have to be bouncing around a lot.
I've also heard there is a fair amount of collusion on there as well but that it's much worse on the PLO tables than the NLHE tables.
If you stick to NLHE you should be alright, personally I just prefer playing on the regular online sites because it's what I'm used to and comfortable with
There are big leagues that are more reliable, but still composed of clubs and so, possibilities of cheating and collusion. I have seen people doing that. The only thing that prevent it to happen is the common sense and respect to other players. In cash games specially PLO is very lucrative if the club is reliable. What makes me keep playing is that the club I am in is the same I play live, so I know most os the field.
Another thing that I like, but you also have to pay attention is the deposit and withdrawals. But the agents every now and then tricks some people.
In the over all, is kind of confusing as you can notice.