I've heard lots of complaints about PartsWerks, but I never had any personal experience.
Assuming that the trend of complaints are valid - at some point they're going to piss off the wrong Joe. Then he'll show up at their front door with a .357 bright and early Monday morning.
I *know* people who don't believe in arbitration through Paypal, small-claims court, etc. Steal from them, and they come hunt you down.
Payback's a bitch sometimes.
-Rusty