I had a so-so experience with Mark. He was very personable, went out of his way to meet me and let me look over his evo
Also was fairly quick and helpful via PM.
I bought a set of 2 piston calipers and some tail lights from him. Nothing critical was wrong with either, but one of the caliper sliders was almost seized and the tails had a small crack. He didn't mention either before hand. I consider both things that could be over looked if one wasn't checking things too carefully.
Bottom line, he's decent seller, just look over everything before you buy it. I think he has so much stuff around that he probably doesn't inspect it all really close before selling it.