Amazon has just launched their MP3 store into public BETA, and after spending a few minutes looking around, and then downloading some music, I'm convinced it's the best store I've seen yet. Highlights -DRM free -256KB MP3s (variable and constant rate) -Browser based... I don't care for an application needed to buy music, especially when iTunes is using 84MB of RAM, just to sit there and do nothing. I use Winamp to play music. -Cheap! Their prices are cheaper right off the bat. Furthermore pricing is based on song length, with "regular" length songs dropping in at around 89c. Albums feature a discount over single tracks. -Flexibility. Apple like doing things the Apple way, that's why there's no Radiohead on iTunes Music Store because Apple refuses to sell full albums without individual tracks being available. You want Radiohead? Go to Amazon. -Simple. Amazon owns ecommerce, there's no step that's not necessary. -Fast! Amazon is building some wild storage clouds (that are available for you if you'd like)... I downloaded an album in at least the same time as I'd get from iTunes, if not faster. And I'm downloading slightly larger files.
Drawback -Only one I've come across is that the service is currently meant for US citizens only. Workaround on the link below.
Daring Fireball has a great write-up.