OK UserTesting.com might not be perfect but it's pretty darned awesome. The rub with this site is that you can very quickly turn around a test with both a video and a written report. The company pays a pool of participants $10 per test & your out-of-pocket expenses are only $30 per 15 minute test.
This is an incredible value considering in-house testing 5 users for 15 minutes will almost certainly cost no less than $300 (assuming a jr. usability professional spends one full day @ $30/hour & users are compensat $10). UserTesting.com cuts that price in half.
Return on Investment
Assuming you've got a team that can rapidly iterate, this is great for a product that's getting tuned or for a product that needs initial investigation. You have to do your own calculations on whether or not this is cost-effective
Doing this testing for each round of iterations would go miles further (and be a lot cheaper) than gathering several coworkers in a room to attempt to accomplish UI design. It's often an uphill battle trying to speak for what users will understand & relate to. But when you have evidence, there can be no dispute. For this reason alone, this has the potential to have a high ROI.
What is it good for?
Usertesting.com has some limits which means it can't yet completely replace in-house testing. Namely, software products it would not make sense for audiences to which you already have immediate access and a low-fi prototype might cause confusion so I'm not sure if that's possible.
Also, I'm not yet sure how long you have access to each video. Anyway, here are the huge plusses:
* Software as a service model means no downloads or storage of huge video files.
* Very quick turnaround--five 15 minute user tests will likely finish within 24 hours.
For live-site testing, this is excellent is an incredibly useful tool to add to the toolbox & look at the buzz they're getting!