As with any other bike purchase--test ride, test ride, test ride
everyone here has their own preference--find what works for you.
To clarify my earlier post, all of my upgrades on my pista (except the saddle) have been purely from choice--i dont get all this "dont get a prebuilt entry level fixed cause you'll have to upgrade anything" stuff. The only exception to this (in my experince) is the Langster--my buddy got one and has had various parts crap out on him. Then again, he also uses his ride as an urban assault bike and kinda invites some of it, given the punishment he dishes out to the bike.