Amazon's shipping record with my stuff is awesome. I even had an item delivered on Christmas day a few years ago, believe it or not.
I also like that they've diversified way beyond books, music and movies. In fact, I probably buy as much non-media stuff there now as I do movies, music and such. Not having to pay sales tax on my purchases is great as well. That's not a luxury I enjoy with Deep Discount DVD, which would be my other main DVD provider.