I know this forum is old, but I read it last night before talking to the graduate director of my school about funding, and I can see there are about 3,000 other people who've checked it out. So re:negotiating for more, my school is explicitly telling me that if I have a better offer I should tell them and they'll try to match it. I don't have a better offer (humanities, 15,000, I'm rolling), but if you were in that situation I would recommend approaching the subject, with a lot of flattery about how much you want to go to their school but have to consider which place will give you the living standard to devote yourself to study etc etc.