I've never used either of those, but I have used Feedback Army and can recommend it as a way to get sanity checks with multiple people. Sometimes it's hard to tell if a certain stock photo is "creepy" unless you launch or use a service like FA, so it ends up being well worth such a low fee (for us anyway).
This may come off as corny but - who is more expert than real internet users?
- I suggest that by being an "expert" (whatever that means) you would have too much 'domain knowledge' to know what would work best from the average internet user.
What I meant by "experts" is people who could look at your site and give it a quick lookover according to their specialty. Web software engineers might look at a site and see code that doesn't validate, or AJAX that could be optimized a bit; UI designers might suggest that you reorder some of the buttons on your page for better ease of use, etc.
http://usabilitytest.com/
Also I saw this service advertised before:
http://www.usabilityfeedback.com/
I've never used either of those, but I have used Feedback Army and can recommend it as a way to get sanity checks with multiple people. Sometimes it's hard to tell if a certain stock photo is "creepy" unless you launch or use a service like FA, so it ends up being well worth such a low fee (for us anyway).