Excellant service for very quick, easy to implement and inexpensive user testing. I agree with some of the other comments regarding the tester pool. Its down and dirty testing so you don't have a lot of control over selecting the panel and the users are pretty broad. That works for our product, but it might not for specific use cases.
Senior Designer, User Experience
E: [address removed]
An operating business of IAC
8833 W. Sunset Blvd.
West Hollywood, CA 90069