I bought mine ~3 years ago--what's known as "Pedal-Assist". My wife's bike, she can just push a lever, and away she goes.
Certainly many more pros than cons. Pedal-assist bikes quit assisting once over 20MPH unless home-built like the previous commenter. A few pros:
1. I take long trips along the beach (sometimes 40-50 miles) and just call DW and she picks me up. Then we have a nice lunch somewhere.
2. With the e-bike, I like to say there are no hills. Even so, I still get a good work-out with the bike.
3. Even as time has gone by, I've not become bored with the bike. Still a lot of fun.
My main Cons:
1. I believe the battery replacement cost is ~$500.
2. There are different levels I can set the battery assist--The highest level is good for only ~40 miles.