I had a tough time transitioning from buying CDs to MP3s. I missed having a CD, I liked being able to look at the lyrics.
Then I got into buying MP3s and appreciated being able to cut down on my clutter - I'm actually sitting here looking at a stack of about 30 cds on my floor that my son went through a couple of days ago.
But then again, I miss the CDs. Easier to load when I change my iPod from one computer to another, and easier to share with friends. And we have a back-up if we lose what's on our MP3.
Of course, there's the storage issue.