Used it a few times to track down parts. Only 2 complaints about it would be directed at the yards and not the service:
Price Changes not reflected. In one case our Bronco II needed a drivers mirror. Local yard stated they had it for 15. Got there and they doubled the price to 30. I told them off. "Why am I going to shell out double the price for a used part when I can buy a new mirror for 20 bucks?" and then I walked out. Haven't been back sense.
Not having items in stock as listed: Same truck will need a motor soon. Another yard states they have 2 "a" grade in stock I called for the price, and the guy states he would need a 600 dollar deposit and two weeks to track it down via other yards. I asked him why the system shows they have two 'a' grade ones in their yard. All I got was silence.
So it's not the service, it's the yards you have to worry about.
Never underestimate the local U-Pull or Pick 'n pull yards. We recently scored a lot of good parts for our Beetle and it's pretty cost effective.
I have used them many times which includes finding my Take 5 Rims. There is a set of Monte Carlo rims here in Dallas that look exactly the same except the inserts and I have those. I can help you look at them if you like. He has had them on Craigslist for some time so I bet he is flexible on the price. VW RIMS 17" MONTECARLO EDITION