I would get one when I get really old (like 70) and can't climb those big hills anymore. I plan to be riding up until the the day I die.
I tried one for about 15 minutes at my LBS last year and it was fun. You can pedal it without any power assist but when you turn it on, you go up an hills with little effort or cruise on flat ground without pedaling up to 15 km/hr. I think the battery lasts a couple hours or around 30km. When I'm 70 and ready for one of these, the battery will probably last for months and top speeds will be around 50 km/hr
Really a nice design. Decent range, fun to ride, feels like a bike. Range is about 20 miles (depending on temperature, hills, speed), but you can switch power off when you're not climbing or accelerating to stretch that. I have one but I don't ride it any more because I like the speed and quiet of a non-powered bike.
BTW: This question tends to excite the purists. Ignore the flames. Get whatever you are most likely to ride.
I got it because I was not confident about commuting 33 miles round trip in the winter in Seattle. It helped a lot when I was getting back into cycling after a long time. You can keep your head up to be aware of traffic and start out quickly at intersections. It's not effortless though. You may still sweat on a pedal electric.
I wouldn't get any excercise riding on a Vespa and besides Vespa's are illegal on the bike paths. When I'm 70, I'd still excercise to keep the fat off and the ol' ticker ticking. An electric assist bike will allow the me, as an old geezer, to pedal it so I can at least get some aerobic effect.
If I didn't excecise, I'd probably turn into one of those fat people you see riding on those electric "fat people movers" in the mall. I don't undertand that. I see them all the time, it's my own personal "sixth sense" ......"I see FAT people!" It's not that they can't walk, they choose not to because I see them get off of thier fat people mover to waddle over to the freezer to grab a gallon of Ben 'n Jerry's. If anyone needs excercise, it is them. I think they should put a set of pedals on those things and disconnect the motor. It'll sorta be like a recumbent with 4 wheels... *****, off topic... sorry... my bad...A.D.D.