nah, you'll be fine with whatever bars you get as long as you're riding in a position that's comfortable to you. bullhorns will be nice for commuting especially if you live in a hilly area since they're very nice for climbing. you'll have to get new TT style brake levers with bullhorns though. i.e. http://www.amazon.com/Cane-Creek-car.../dp/B001PLUZ5I (those are carbon and pretty expensive, you can get em for around $25)

i'm not personally a fan of risers, but then again i've never really ridden them. bullhorns just offer more riding positions.

you should also note that the sst al comes with aero brake levers that offer a bullhorn-esque forward riding position. you can sorta see it here: http://4.bp.blogspot.com/_j5rsUB3wTI...o/s400/cc3.jpg
how he's in a more upright position, if you look at the pic of the sst al on BD you can kind of imagine how that position would work