Can't say you don't have a valid point. But I've had good luck and enjoy it very much. The parking is really the key for me, just pull up, pop up onto the sidewalk (if wide enough) and go. JCPA has been great and leave me alone.
Plus, they look so damn cool. Especially when you waive at people and say ciao.
I'm more concerned with the blind corners, non-working traffic lights, crazy-ass JC drivers, Fresh Direct trucks, lost idiots looking for the Holland Tunnel, and of course the complete disregard for pedestrians and traffic laws.
Where does one keep a Vespa in the city? I would be worried someone would pick it up and walk away with it.