I thought this was a pretty good write-up.
As for scooter forums, I know of these:
If you're just using it to get around the city, you probably don't need a 150cc scooter. A lot of the newer 50cc models will do 35 or 40 with little or no modification, and I think that should be plenty fast for "in town" stuff. In most states, vehicles 50cc or less do not require a motorcycle endorsement on your license. In some states, no insurance is required, and in some states no registration, title, or plates are required. You should check your state's laws, but it's worth looking in to.