a dual core i7 laptop and two weeks of non-stop mining, and i got a block ! woot. now i just have to wait for the price to rise again. 
ypool might get you 2+XPM/day.
no more than 0.2/day I think
I'm averaging 2+XPM/day with mumu's latest miner. It's well worth a shot if you're not hitting blocks solo. They now have a system that runs like PPLNS. His new one uses mikaelh's updates as well.
It uses gmp?
Yep, they added it a week ago:
https://github.com/jh000/jhPrimeminer/commits/master