#1 Good customer service
#2 Fast cashouts without hassles.
Having done a lot of playing those are my top 2. Yes, I prefer some software over others, but I will always choose the better customer service and fast cashouts over the software. (Kudos to Profitshare for their instant cashouts.)
Also, someone from Cryptologic was on a pannel last year where he said that if you can’t explain your bonus terms in 3 short sentences then it is too complicated. Amen to that.