Sold my iphone 4 to them got exactly as what the website quoted. If you want to get rid of something quick I definitely recommend them, otherwise you might try eBay, Craigslist, etc.
I had a very good experience with Gazelle. Sold my iPhone 3GS for $163. Perhaps I could have gotten more on eBay, but sometimes eBay is not worth the hassle. They didn't lower the price from the original quote and I received check in the mail within a few days.