I've had my tree on there for just over twelve months and have made contact with about 6 (distant) relatives. I have 590 people in my tree though so that will obviously increrase the chances of finding soneone related.
Have had some contact from people on GenesReunited, but didn't go as far as I would have liked it to.
I found UK People Finder to be brilliant. I found a long lost nephew who was adopted 40 years ago. Mother & son are now reunited & a family is complete. A wonderful story ever to be told!
I found quite a bit out about my dads side of the family although Im lucky enough to have a fairly unusual surname so it wasnt hard really. One thing I did discover it that through generations the spelling of surnames was often altered slightly (as people were illiterate) so that can put a spanner in the works a bit. Good luck with your search!