The venerable Deutsche Grammophon, premier classical music label for decades, has opened a web store that comes pretty close to doing everything a classical music store should do. First, the files are 320kbps mp3 files, without any DRM. The interface is pretty good, and when you buy an album (generally priced at $11.99), you can download the tracks individually or in a zip file. Finally, and best of all, many of the albums come with the original CD booklet as a PDF. This may not matter as much for Beethoven symphonies, but for new music, such as DG's excellent 20/21 series, the liner notes are very valuable. The iTunes store sometimes has digital booklets, but only for hot new releases. The 20/21 albums are available in iTunes, but at lower bitrates and without the booklets. The additional value here is tremendous. I wish all new music labels would include the liner notes with the digital releases.
In order to make the store really killer, DG should release their immense back catalog. As far as I can tell, they are only releasing items that have appeared on CD. Except for an odd track, such as Gerd Zacher's recordings of Ligeti's organ music (which were re-released as part of a bunch of Ligeti albums), I can't find any trace of the superb Avant-Garde recordings that DG released back in the 1960s. Other works which haven't had a CD reissue are not to be found as well. I had a record of two Luigi Nono works, Como una ola de fuerza y luz and Y entonces comprendio, one of which featured a hot, young, up-and-coming pianist named Maurizio Pollini. Como una ola... has been reissued on CD twice as part of various Pollini editions — both albums are in the web store — but Y entonces comprendio, which was for six female voices, chorus and tape and which didn't feature any stars, still languishes. Nevertheless, this is a great start, currently the best source for downloading classical music.