I bought mine from Staples, but Amazon has provided great Customer Support for my Kindle anyways. In fact, when there was a problem, when I experienced freezing issues, they offered to replace it with one-day shipping for me (but I fixed the problem myself by removing the nonlighted leather case)
If Amazon doesn't charge you taxes for your Kindle, definitely buy it from them. It makes quite a difference. If it doesn't, consider buying it from Best Buy since you will get it immediately, and you can easily return it (without paying for shipping) if you don't like it. In addition, I heard that Best Buy is offering free cases with the Kindle (but that deal might have passed).
If you buy a Kindle from Amazon, please click this link
before you proceed to checkout. It won't affect you in any way, but I will earn a few bucks that I can use towards buying eBooks