This seems to be getting slammed pretty good in most of the comments, but I can see this as being very useful especially when purchasing tech items. Case in point, I have gone through several wireless routers, mostly because some of them really really suck, and some are fine. What am I to do when I don't know what is in stock locally and I want to know if the specific model I am getting is crap or worth buying? Go read reviews on Amazon, etc.
How do you know which of the 10 motherboards in stock at Fry's is a total piece of crap? Go home and read up on them? Sounds like a super way to spend time, going back and forth to read reviews when you need a computer up and running ASAP, but don't want a brick in a month.
While perhaps not a killer app, it would be something I would interested in. All assuming you can focus that close.