I know this is completely anecdotal, but I've been a Goodreads user since before Amazon purchased them, and I have found that Goodreads reviews are way more accurate...or, more accurately, they don't have as high of a degree of skew towards very low or very high ratings.

It's definitely changed my buying behavior on more than 1 occasion. I have to imagine it's a big driver of sales, otherwise, as the article mentioned, Amazon would have made much larger UX changes post acquisition.