I've had 7-8 claims that paid out for varying amounts - certainly over a grand in total for people using shots of mine that I honestly didn't even know had been used. That being said, this was quite a while ago, I've lodged about 5 claims in the past 3 years (not reduced because i've not been producing, but because I've only a free account, and it's only looking at old stuff) and to be honest, 3 from 5 they've given up at the first hurdle, and the other two they took around 6 months before deciding that their cut wasn't going to be sufficient to pay for their time in chasing) - that coupled with pretty much every hit I get now seems to be hosted somewhere that they can't chase means it's not really something I spend any time on actively anymore.
still - it was a free account, and i've got some brass out of it in the past, so its all a bonus.
If I was actively producing work then I'd quite possibly entertain giving it a go on a paid membership, but at the moment, what I'd really like to know is how on earth I can delete the photo's in my current database and add a more hand-picked selection to search for - when I signed up i fed it links to things like flickr and in all honesty, most of the stuff it has been searching for has very low or no likelyhood of being used by anyone for commercial purposes, and therefore not going to generate a hit.