I note with interest that Amazon have recently launched their MP3 store:
I have to say that this look rather good, for the following reasons:
1) Most importantly it is DRM free (which always puts me off buying from itunes)
2) It's cheap - there are brand new albulms selling for just £3.00... and not rubbish albulms.
3) It has a MP3 downloader software (which I haven't tested), which automatically updates itunes for you.
4) It has a good selection from the get go.
5) It's Amazon, so if you have any hassle, you know that their customer service will be top notch.
So, all in all... Looks good.