Lot of comments putting this service down - but I love it. I used them for a beta launch. Got ~180 people who applied for it. Got a ton of honest feedback that helped me plan for my next beta round.

The actual website is a bit slow and not so intuitive, but has a bunch of features. Support is great.

Having people put in their device UDIDs makes the process faster to register in the Apple dev portal.

There are other services I'm planning to try out, like http://erlibird.com and http://playtestcloud.com. PlayTestCloud will record audio (maybe video?) of people trying out your app/game. I imagine it depends on the capabilities of the device OS though.