ENWorld has a good post about reviews...a plea for more, really. I posted a comment there and then realized I have an open post spot for today's blog and should relay that thought here, too. So:
My general experience with reviews in this hobby (and no doubt others) has been along these lines, however: people usually post reviews of product they like, or were predisposed to like. It is not too often that you see a critical or negative review unless the poster was already predisposed toward disliking the product, or was so amazed at how much he disliked it that he needs to share his experience. Gamers seem to be notorious for judging a product after reading it, but far less often actually discuss the product from an actual play session, or even just attempting to work with the mechanics. On my own blog I tend to string out game discussions on product to several posts, exploring facets of the rules and leading up to an actual play experience. I have found I am rarely disappointed that even the cleanest ruleset reveals some interesting warts once actually engaged with at the table. For this reason, review posting online is good....but the typical results of those reviews do tend to follow Sturgeon's Law in both directions (for both the quality of the products and the quality of said reviews).
I'll point out one thing, though: no one has quite managed to capture the lighting-in-a-bottle with a review process that is Amazon. Hell, I may buy mostly on site X, Y and Z but I always go to Amazon first to read the reviews. Every online site that aspires to provide useful reviews should look to the way Amazon does it as a model to aspire to.