For the Love of Reading - Do Reviews Make a Difference?

I wish I'd remembered to add "Good Reviews" to my poll. But I just had an incident that reminded me of my oversight.

I was at Fictionwise, looking for a book I'd seen promo'd on one of my umpteen kajillion e-loops. The premise looked interesting, and the author had gotten some great reviews from notable review sites. However, over on FWise, that same book had one or two (maybe) Great ratings, a few more Good ratings, but the remainder were Fair and Poor. Most of her reader reviews were in the lower ranges. Needless to say, I'm holding off until I get word of mouth from some people I know and trust to let me know if I should fork over the money.

Not too long ago there was an uproar about authors and their fans manipulating the reviews over at Amazon, which led a lot of readers to reply that there were ways for the authors to have low ratings removed. As such, the reviews at Amazon are not as unbiased as they could be. That's not the case over at FWise. What authors get is what authors get.

So, my question is this... Do you trust reviews? Do they make a difference when you get ready to purchase a book? Are there certain sites you trust more than others?