I, too, have an aluminum flywheel (mine is 10 or 11 lbs.) I have put about 30K miles on mine and have also had no problems with warping. I also agree that it is one of the best mods I've done. You REALLY feel it in 1st gear - redline comes up MUCH quicker. And 2nd gear is VERY strong. Don't really notice much different is 3rd, 4th, or 5th, but it was worth it for the stronger pull in 1st and 2nd.
I think I'm goin to have to do it. My car isn't a huge horsepower monster. I'm not goin turbo either. It only has CAI, hotshot headers, greddy sp and s3 cams. While I'm doin the flywheel I'm also picking up a JWT clutch kit. I was thinking about JUN flywheel, but I dont have that much cash. Also I only want to drop the tranny once and get it all done. Only thing I will have left to do is JWT ECU and I think I'll be done for now. Maybe some nitrous later though