hapax legomenon - I have no idea how the MP3s work on Amazon for indie bands but personally I think it would be really neat to be able to sample and purchase tracks that way. The prices at Amazon are great especially for 256 kps sample rates and the selection is ever expanding. The biggest factor for me is NO STINKING DRM.
That's why I stay away from itunes, it's easier for me to buy the CD and rip than to have to convert itunes purchases.
Unbox is a lot of fun, it's easy to download. My only qualm is that you have to use a special Unbox viewer to watch. If Amazon stops supporting Unbox I bet that any purchased shows would be unwatchable. I've had some problems with rentals but Amazon has been quick to offer solutions or a refund. The downside to Unbox is that it's only available in the US and TV is pretty much limited to NBC/Universal.
Maybe Amazon is becoming the Borg.