I had 2 magazines converted, and am very pleased with the work. They still hold 10 rounds, feed perfectly, and have a nice flush fit. I mentioned that I have a black pistol and he put a nice black finish on the bottom plates, too.
See for yourself:
It's just a flat fee of $20/magazine; you provide the original magazines and ship them to him with payment, and he'll do the work and ship them back. He also included a nice hand-written note saying if I had any problems, he would buy a new magazine for me.
It does take a slight smack to get these magazine to catch the latch, but unlike the stock mags, they don't wiggle once they're in there.