Here in Colorado you do have to carry vehicle insurance and you do have to register the scooter. For full coverage I'm paying about $120 per year. My registration is for three years and cost about $6. You get a little sticker you apply just about where the plate would normally be. I will note, at least here in Colorado the odometer reading is not noted on your registration and I made a smaller sized copy to carry along with my insurance card. You never know when you'll get pulled over so it's best to be prepared.
I will also note that you probably won't find a shop that will work on these. You'd better learn how to repair then including replacing tires. Luckily they are simple to repair.
I got an app on my Droid that I keep track of fill ups, and mileage. Here is the average over the last two months. I will note that I have to take the odometer reading and convert it to miles since the odometer measures kilometers.
March was the first month the scooter was registered. It was also during the break in period which obviously didn't have the best mileage.
Now, in April the break in period is complete and now I'm getting full MPG's. They are great!