I had a 6 disc changer in my old Acura... I liked it for a while, but frankly, doing chinese-fire drills at stop lights to change cds (it was in the trunk) got annoying. I always tried to install customer cd changers within reach of the driver, or a passenger ~ so there is some chance of changing cds while in the car. My problem was, I was too lazy to change cd's, and would get sick of hearing the same 6 discs, but could never change them until I got to a reeaaaaallly long light.
But I will say MP3 players rock! My Kenwood is CD-RW compatible, so I can burn disgusting amounts of music over and over again... only problem about MP3 is the decreased audio quality ~ which you really won't hear unless you have a good system, but if you have good highs, you'll most definately be able to tell that its an MP3!