Does anyone has testing experience with Ubertesters community?

Hi, I just wonder if someone from you guys hired beta testers from Ubertesters. Ive been using their platform to ditribute the builds, get bug and crash reports, and quite happy so far. But now I was thinking to hire their testers to help me before going public. Does anyone have experience with hiring their testers? If yes, whats your impression?

I did use their testers for one of my customer`s app, it worked well. We hired 15 testers and indicated devices/OS that we wanted to test on. The app was pretty simple, we just wanted to check how it looks on various devices and get the user feedback. We discussed the requirements with their PM and they get started the next day and provided the results - bugs found and feedback, the same day.