I've had about the same results as KC. If you're looking to create buzz, it's a good outlet. Of the 3 giveaways I've done on GR (for 2 books, 1 book, 1 book) I had 800 - 1000+ people requesting. OTOH, if you're looking for reviews, try book bloggers and review sites instead--you'll probably have better luck at seeing a review from your efforts.
~ Award-winning romance with an edge ~
Generous samples are available at My Website