i rode one for about a month or so. its only my opinion, but i think a road bike is just as good, if not better. they are very heavy, and the charge eventually runs out of course, so you have to be able to store it where you can plug it in. the batteries come off of some of them so you can carry it and plug it in, or prevent theft. however, the batteries themselves are quite heavy, and carrying it around while shopping or something is not very realistic. there are kinds that use levers near the handlebars that power the bike, or ones that use the pedals to create power. i know i am not very good with bike terms, sorry! i never remember the names of things but i always remember what they are and for, which doesnt help me explain it, i know.
the upside to them is you can go faster with less work, of course, but not too much faster than a road bike. i could get up to around 30mph (no computer) on flat road. its much easier on the body for a long commute (if your particular battery can hold enough juice for a long commute!)
the downside is they are HEAVY. if your battery runs out and you arent able to recharge it, you have to ride with the dead battery which can be very challenging on the hills, if not impossible on some steep ones. also, you have to be very careful with rain. they usually come with covers in case it rains, but you cant get any water on the battery ever.
however, i have seen ones with pretty small batteries. maybe they are lighter, i dont know.
i stopped using mine because i just wasnt enjoying it. i worry about everything, and i did not like stressing about how i was going recharge the battery, and how much juice it had left in it everytime i left. also, i had a few technical problems and ended up having to take the battery in a few times.
one more thing, they attract a lot of attention. people will be staring at you. i personally hate being stared at, but there are lots of people that like it!
but thats just me. :P hope that helped a little...