If you send your surfer's to a quality site that has quality content, does not play billing tricks, updates as they say, then your surfers will be happy and your sales will reflect that.
Obviously it's impossible for an individual to review each and every paysite out there to know if they're full of crap or not.
I suggest using one of the many paysite review sites for surfers, and use it for your own guide of what paysites to promote.
Here are two that come to mind..
http://www.adultsitesurfer.com
http://www.thebestporn.com
Cheers,
Matt