Honestly I don't see the Amazon store making a serious dent in the ITMS market. They need to do some serious work.
I was quite interested when I read about this today. I registered an account with amazon.com to try it out (they wanted an email and username only).
I went through to buy a track. Selected the track. Declined to download their software (since I was trying it out). Got to the purchase phase. Pulled out my credit card, typed in the number and expiry, clicked next.
Then I got to the shipping address (which is required for the CC to be approved), and they only allow you to enter a US address.
Nowhere in any of the leadup was there any mention that this was going to be US only, something that Apple is quite upfront about.
It seriously pissed me off that they raised my expectation, took my credit card number, and then wouldn't sell it to me, with no warning. Worse yet, they never once told me they wouldn't sell it to me, they simply made it impossible to complete the purchase -- the box that I finally failed on was even labelled "State/Province/District" then simply only had the USA State abbreviations. I sat there for a minute trying to figure out if I was missing something.
99.9% of the world doesn't care about DRM. Apple has such a head start inside USA that everyone else is already fighting for dregs. The fight is now for other parts of the world.
Seriously pissing off your customers by refusing to admit they even exist is *not* a good way to break into that market. In the future I will be willing to pay an extra 10c for a better experience from another company.
Amazon had the chance to take me away from Apple, or even put me on a waiting list to be taken away -- I understand the licensing issues, a screen at the beginning saying "Due to licensing issues, the music store is only available to residents of the USA" would be enough -- but instead they not only drove me back to Apple, but upset me enough that I won't be going back to try again.