It was a really weird feeling the first time I stepped on the treadmill with them, since they are much lighter than my old shoes, the Asics Kayanos. The first thing I noticed was that I wasn't striking with my heels as much -- that's a good thing.
They're much lighter. I know I was having lots of pains with the Kayanos toward the end, and they eased up almost instantaneously with the Precisions. The shin pain has been coming and going but I've barely had any knee pain since I got them.
I've been very careful, my weekly mileage is skyrocketing up with the marathon training, and overall these shoes have been a very good partner. Lighter has been better for me. Who knows, maybe I will become a barefoot running convert someday!