I have ordered a total of 3 sets of calipers, brake hoses & semi-metallic pads from Muskegon, and so far I am very impressed with both the parts & the company. I ordered my first caliper after meeting them at Bloomington Gold 2001 (very friendly & helpful people). Then in July of this year I developed a leak in my other rear caliper and ordered a replacement for it. Unfortunately when I bled both rear brakes, I found that the 1 year old caliper had a faulty bleed valve and would no longer seal. I called Muskegon and they replaced the caliper free of charge!
In typical Shark fashion, my third (left front) caliper then decided that it wanted to be replaced too. It was just 4 days before Funfest, and Muskegon came through for me again, with time to spare!
All in all, I highly recommend them as a parts supplier (same parts as Mid America & Corvette Central, but quite a bit cheaper). I might also suggest that if needed, go ahead and replace your calipers in pairs, because once one goes bad, the others are sure to follow soon!
Good Luck!