The interface; the fact that it's both limiting and inspiring at the same time, and of course samples don't really convey the interplay between the sounds when you sum everything to the same single output. And of course, this lil' bastard runs on batteries so I can just take it to the park in the summer and blast it through a ghettoblaster
A software emulation would be easier to integrate (not to mention cheaper) in many ways, but I simply find it infinitely more inspiring to have a dedicated box & controls. If that makes me do more music, it's well worth it.
Also, street cred