Ask HN: Mechanical Turk and beta testing

How many of you have used Mechanical Turk for beta testing?

* Have you guys gotten any real value out of it?

* Do people really come back and tell you what works and what doesn't?

* Has it been effective in fixing bugs or improve funtionality or usability?

* And does the reports help in determining the usability of your app?

Thanks in adv for your input.