The best and lightest ebike on the market is the (pedal assisted) Giant Lite. This is the last year of production.
I bought one used for a little over 1/2 price of new; $800. It got me off my 60 year old butt and into a FUN commute. My knees don't hurt anymore and I can fight any headwind or hill and load it down too.
If I want a better workout, I just gear up or turn off the assist. If I'm smart with the use I can get 30 miles from a charge and that is as far as I care to ride. My commute is 12 RT. I can average 12-15mph with out the traffic lights. I enjoy it so much now (biking) that I'm selling my little used Cannondale.
I find most who knock it, haven't tried it! But then, "I'm here cuz I'm not all there"