Electric Bicycle Information - Types of electric bicycles, legal status, and links (pdf) Some info and links may be out-of-date.
I ordered my Giant Lite online without any opportunity to test-ride one, and wasn't really sure what to expect of a pedal-activated bike. It was described to me as intuitive, awhich turns out to be a good description, along with elegantly designed and a lot of fun. You don't have to give any thought to the power assist; it just comes on naturally and eases off naturally as you get up to speed. The Lite feels like my road bike did when I was 30 years younger -- fast off a start, quick down the road, and a pleasure to ride. For the first time ever, I can go on a long ride with my husband, a strong biker, and stay close!
I was interested in the bike for two main reasons: my knees don't deal well with taking off from stops anymore, and I need to carry heavy loads to work fairly often. (Gas prices helped too.) The Lite has performed beautifully to solve both these problems. The power assist seems designed to give the most assist from a full stop, so taking off is a breeze, and I feel considerably safer getting through intersections fast. And I can now carry 30-plus pounds to work without even noticing it. I find this a very pleasing solution compared to driving a 2000-pound car in order to carry 30 extra pounds.
In addition to commuting to work, I bicycle for exercise and was concerned that I would not be able to get much exercise on it when I want to. This has not turned out to be true because I bike further and more often, there are several ways to control the level of power assist, and I frequently turn off the power when I'm on the level. On a long ride, the bike tends to top out around 18 mph when the power eases off, and that provides steady exercise under your own power. (Don't expect to keep up with those pro bikers, since the Lite is heavier than most road bikes, so it's sort of self-limiting around that speed.) In general the exercise I get is even and feels like it falls in a good target heart range, but doesn't go above that range as some intense exercises do. (If I feel a desire for intense exercise, I can turn off the power and get that too.) I would think the Lite would be ideal exercise for many older cyclists.
In general, I find this bike has extended my options with biking and made it more attractive -- I can carry more weight when I need to; I can go easy when I need to; I can get exercise when I want; and if the day has just been too long, I can take it easy and ride home with help all the way.