I'm researching it more now because my goal is 33% mainstream (and 33% cams/dating + 34% paysites) by the end of 2011. I used to do quite a bit in mainstream many years ago but it was a different time then (pets.com, etc). Ironically I left mainstream affiliate marketing in 2000 because adult was more profitable.
One thing I notice is that the conventional wisdom even today is basically that if you send 200 uniques and don't make a conversion, stop promoting it because it isn't worth it. This alone shows you an apparent major difference between mainstream and adult. Imagine doing that in adult. Well it used to be common....but back in 1999.
