I have a newly minted M on my license… and a whole 10 hrs of sitting in a parking lot on a 250… but when I was a kid I had a couple days on a Vespa and it was very natural. Sooo….. I am about to buy a 2006 Honda Silverwing Scooter. 583 cc and owners say it will cruise at 70 on the highway. I took my intended for a short ride down a street and if anything it is too nimble. The 600 lbs is largely concentrated at hub level so the bike leans really easy and I think would be easy to pick up if dropped…. but it is not hard to keep vertical in the parking lot or on a neighborhood street. Hi-way remains to be tested – after I learn to ride the parking lots and back streets.
As I see it the main advantage is that there are no gears – twist to go, breaks on left and right hand just like a bicycle, feet just brace. So I can concentrate on traffic, lean and road until those reflexes become more natural and automatic. Once I know I won’t get frightened away from riding on the road I may consider a “real” bike with gears – like a Goldwing. Or I might stick with big scooters and driving comfort. 
