Just wanted to share my experience riding a scooter in Italy a couple weeks ago. I was in Rome, Venice and Florence, and rented a scooter in Florence for a day. It was fantastic.
First of all, they're everywhere. If you stand on a busy street corner in the city for 2 minutes, you're bound to see about 15-20 of them. Seriously. It was awesome to park my scooter downtown in a row of 50 or 75 scooters.
Most of the scooters are NOT Vespa - there are a lot of Hondas and other brands. Almost every scooter has a windscreen, most of them medium or tall. Everyone seems to wear helmets, but most are half helmets with no face screen... at least that's what I saw in the city.
The best part is that lane splitting is normal. Whenever there's a red light or a line of cars, all the scooters work their way through the traffic to the front of the line, and when the light turns green, off they go. So much fun. Even in city streets, where cars are lined up at corners for turns, red lights, etc, the scooters just go around them.
It's really hard to come back to the US and sit in a line of cars after the Italy experience... I'm just dying to scoot right past them all and move in front.