Topic of conversation around here too. I don't want one - I ride my bikes partly because of the effort needed to burn some Kilojoules and riding is by far the most enjoyable form of exercise I can find. And that I'm a two-wheel junkie with zero interest in cars, gyms or running. :-)
My Mrs OTOH has a busted knee and has given up riding because of the discomfort. Why hers is right over the back in the pic below. Electric assist could get her back out with us. I like this UrbanX idea for her situation. She's already got a nice Electra Brand cruiser:
