My Met's engine displacement is under 50 cubic centimeters, which means I don't need a motorcycle license to ride it in Massachusetts, just a regular driver's license. It also means that I can legally ride it in the bike lane, which is what I do when traffic is backed up, a great way to draw angry glares from drivers. Parking is never a problem; I can legally leave it on the sidewalk.
Boston's weather isn't exactly the most scooter-friendly, but I managed to make the commute on most days through the winter with a pair of ski pants, warm jacket, and fleece, and, on days when it got below 20 degrees F., a balaclava. When it rains, I wear a rain suit. The only time I don't ride is when there is snow or ice on the ground.
Boston drivers are legendary for their aggression, so those of us on two wheels definitely need to keep our wits about us. On the plus side: I've given up coffee, as I'm wide awake by the time I get to work.
As for protection, I wear a motorcycle helmet and a good pair of gloves. Some scooterists I know go all-out, with motorcycle boots, kneepads and sliders, and armored jackets. But it seems that most of us take our chances with just a helmet.
Did I mention the gas mileage? Every week and a half or so, I put about $2.50 in the tank. Lately, it's been more like $2.70.
From an environmental standpoint, not all scoots are equal. Most older models and some newer ones have a two-stroke engine, like an old-fashioned lawnmower or a chainsaw, which requires a mixture of oil and gas. You can identify these by the puff of blue smoke that belches from their tailpipes as they accelerate. These engines, while generally having a little more zip than their four-stroke counterparts, tend to have terrible emissions. In 2006, the Oregon alt-weekly Willamette Week looked at emissions from two two-stroke scooters and found their exhaust to have far more unburned hydrocarbons and CO2 than an SUV. Granted, SUVs put out a lot more exhaust per mile traveled than a scooter does.