I recently purchased a 3 week old one on Craigslist. Some parents with more dollars than sense bought a phone for the their teenager and within a few weeks he wanted an Android he could hack instead. Anyway, I got mine new in box for $55 and LOVE it.
There are a few materials that it doesn't like, but so far I have not had issues with it. I really like that the phone stays at 100% until the case battery is depleted. This dramatically reduces charge cycles on your phones internal battery. I have not had a single instance of my phone getting below 50% since i started using this.