I personally don't give a shit about MP3's. It's good for prelistening a CD if I consider purchasing it.
For me it's exactly the same as for Gast1 and that french hippie: I want to touch it, feel it, read the lyrics and booklet, admire the artwork of the cover, back and inserts and most of all some tangible piece of art of which I can be proud of to possess!
But hey, I'm just an old(fashioned) bastard (31 years).