Don't buy it at Best Buy -- Amazon's return policy is far, far better. I know people who went through four Kindle 3s at launch and returned them all without any issues. You won't save anything on shipping because it's free.
The reason to go to Best Buy is to try one out to see if you love it. That was how I learned I needed an eReader -- by trying out a Nook at my local BB.
I check out new laptops while I'm there as well but never buy them because BB is known to swap out parts.
Smartphones at BB are another matter.