Depends on the program, but here are some anecdotal information.
1) GRE doesn't matter. My PI's on the graduate program's admissions board, and he says the first thing the committee reads is the recommendation letters. GRE matters very little to them. As long as you can show that you're competent through the GRE, they're more interested in your research abilities.
2) GPA is fairly important. I had a friend with a 3.4 from a difficult engineering program who was interviewing at a top-tier PhD program. During the interview, the interviewer directly asked him "why is your GPA so low?" He ended up getting in, but I think it was a close call.