I have a kit from
http://electricrider.com/crystalyte/phoenix.htm and I really like it, they are pretty honest about their top speeds and range, I've ridden the Currie bikes, and wasn't overly impressed with them, mostly due to their low top speeds (15mph) and their motor felt a little weak on acceleration.
I also have a Tomos Arrow scooter, made in the chec republic, they are slightly lower quality then Honda's but not much, they are good enough that I bought one new, if you check on eBay there is a guy selling some 2005 models, that is what I have, carburetors are the most worked on part of a scooter or moped, and the Tomos has a single simple, easy to remove cover that bolts on that covers the carburetor, you can buy new parts for them from Tomos, and new and after market parts from places like MopedJunkYard.com, also if you check on mopedarmy.com people tend to like Tomos, if you are looking at old stuff tho, find a Puch or Honda on craigslist.
if you can get a motor cycle license,then go for a small Honda motorcycle, even the oldest ones you can find work well and are cheap to fix.