i tried it, moreover used it for a year, it was a pretty steady income if you ask me
then i lent my account to a friend, he also used it for a year, then all of a sudden it has been converted to percentage payout, which i can't really understand, because there were absolutely no problem with the quality of the traffic, he has driven even higher quality than i did, so that's my review
i've never asked the reason of converting, they've never told it either
but the percentage program isn't bad at all, you can make more money with it than with the PPC program