over the years, It's become more of a feel thing for me. I started out wanting to look cool, as with everyone else.
However, in the last few years I've started going to two extremes; super-high or super-(ish)-low.
When I have it low, it feels more "right" for the rockin' stuff, since I like the fact that I can really beat the shit out of it, and put pretty much the entire body in to my playing. It's more intuitive, I guess.
When I have it high, it's for the technical stuff, plus it's kinda necessary with the 7-string, since I have fairly smalle hands.