I like that it's easy to find bugs with this application, you can have different people from all over test your website or app at once! There are some things in our platform which we need more time for fixing them as well but overall usabiestesting has been great so far!! Nothing really bad about using their product because they provide good support when needed too. We use USABITEST mainly testing websites' performance before going live by multiple testers around world via cloud webinar service (which was also provided by userbites).