I also prefer rear usb / aux inputs. Keeps the wiring (and usb drive /
ipod, if you choose) out of sight. I also have a standalone satellite
radio receiver (suctioned cupped to the windshield), so the rear aux
input let's me cleanly "hardwire" it to the back of the receiver.
(cable is routed under the dash through the back of the dash pod)

Pandora is great. And a few head units allow you to control it
directly, so you can - view artist / song, thumbs up/downs, etc on the
display. (But this may be only for Pandora running via iPhones.)

As far as controlling your USB / MP3 / iPod via the head unit, I think
the practicality of this varies between head units. I have a Sony with
a single line display in another car, and controlling the USB drive is
useless. I think units with multi-line displays may make it a better
experience. By ditching the CD drive (or using a flip-down face) and
eliminating things like radio pre-set buttons, some displays are quite
large:

http://tinyurl.com/4x5yehl

Personally, I never listen to CDs anymore and because my van is for
road-tripping, I don't listen to "terrestrial" radio. So maximizing my
digital music / sat radio experience and keeping things as
tidy/concealed as possibly is priority.

Oh, and yeah, Crutchfield is great!

James V
86 Syncro