yeah, really look at how the bullet comes out of the magazine. Maybe file it down a little bit and try to round-out the edges of the inside of the magazine where it feeds. I also opened the top end up just a little bit(made it wider), at first it was too wide so I had to go back and knock it back again, but I kind of "nailed" it and I am not having any problems feeding the rounds from the magazine anymore.
Also, I noticed that when I was releasing the slide-release my hand was toughing the slide, and that was "slowing" it enough to make it too hard to get the round out of the magazine. After about 700 rounds, I am very happy with the performance, some rounds still seem to feed differently than others, and I think it has a lot to do with the shape of the rim, but the magazine was key to getting mine working nicely, nothing wrong with the pistol itself. If you still have problems feeding, try to find a similer spring that isn't quite as strong, and try it out in the pistol, or you might be limited to 9 rounds, because 10 might put too much pressure on it to feed.
Had the same problem with my mags and I tried to overcome them for months by lightly oiling the mags after each shoot but they became progresevly worse, untill I couldn't take it anymore and I sent them back to S&W for exchange. They sent me back new clips with the letter A on them and the gun is operating flawlesly. Send to:
Smith & Wesson
2100 Roosevelt Avenue
Springfield, Ma 01104
PS: About a week turnaround.