UserTesting is a great site, the program works well, you get paid for your work (the best I found so far), and it's actually fun to do. I had my first live interview and it went really well, the client appreciated my feedback and I felt good that I could make a contribution to something. The interface is easy to use, and payments came through no problem. I highly recommend it. If I had a product that I needed feedback on I would also recommend it, you have access to a vast network of people and you can screen them for specific characteristics. (Note: I use the browser version on my laptop, so far I have not been accepted for any tests on my Android)