After some use, I definitely see the direct and immediate value of getting feedback from an alternative perspective. I'm hearing people question the credibility of the reviews but I don't think that's the point. If someone tells me my header graphic is illegible or my site doesn't display in IE6... that's helpful as is.

That said, this feels a bit like a Ponzi scheme in the sense that I'll only get reviews as long as there are new/active users... I could see that being a long-term issue (as with any site following this model).