I'd prefer to have all the work done for me and just buy the prepared CD but when there's no other choice but to buy as a download then that's a different story.
I've recently started buying scores as downloads: some of Jeremy Soule's recent game scores from
www.directsong.com and Chris Tilton's score for Black. And I can't notice much of a difference in the sound quality compared to ordinary CDs (though I have to say that some of the Soule scores are available as 320 kbits/sec). So I'm coming around to the usefulness of the download purchase.
What I don't like is being tied into iTunes and having to use them to get a score I'd want. I'm holding out hope that Mikael Carlsson's store -
www.moviescoremedia.com - starts offering their download releases iTunes-free like
www.directsong.com do).