I had a partial tear in my quadriceps (vastus lateralus, on the outside portion of the thigh) for both legs in February 2009. I took several months off leg training, as well as physical therapy to recuperate. I have been slowly building my leg strength back up over the past few months. Neither my doctor nor physical therapist can give me a straight answer on how hard I can push it now though. The physical therapist says I should be able to start going heavy again but it may not be safe for me to push it as hard as I used to. My doctor says I should expect to be able to do no more than 90% of the weight I used to use. I was doing full squats with over 600 lbs. before my injury. I would like to get back up to this weight and go even further in the future.

Am I going to be able to continue serious powerlifting after this injury, or am I just screwed? Anybody have any experience or suggestions in working past an injury such as this? Thanks!

There's no reason you can't come back as strong or stronger than before if you do things correctly. Jim Hoskinson completely tore both quad tendons and came back to squat 1100+ in competition.
First, make sure your range of motion is good and you don't have excessive scar tissue in the area. Some ART or deep tissue massage could help if you have too much scar tissue in there.
Work back slowly and don't try and gain back your old strength too fast. Also, make sure your technique doesn't put excessive strain on the quads. So make sure your knees don't travel forward when you SQ and push your knees out and sit back. This will put a larger portion of the load on the hamstrings, glutes, and hips so the quads don't have to handle the entire load. Also, SQ to below parallel, but avoid the super-deep stuff. I would also stretch the quads regularly.
So in summary, work back slowly, adjust your SQ technique if needed, stretch, and take deload weeks occassionally so you don't end up injured again.

Agreed, just work back slowly. The doc and pt won't be able to tell you exactly because it's your body. You will need to start working your way back up and if something hurts (you know, bad hurt) then stop and rest it until the next workout. Injuries suck, I was just training for a strongman comp and tore my calf and one week after that finally healed I strained my rectus femoris pretty bad squatting. Sucks, competition is not happening now. You know your body best so really listen to it and work as hard and smart as you can.

Thanks for the replies guys. I have been getting down about what the doc and PT told me, so this is definately encouraging.

quad tears suck and always linger