It all depends on how you build the bike. I just converted a nice road bike by adding a geared rear hub motor. The geared motors (vs. direct drive) have a freewheel built in so they don't slow you down when pedaling (direct drive hub motors have a cogging effect when there is not electricity). And a geared motor is smaller, therefore less weight. In fact, I still road the bike normally after putting the hub motor on, since I had to wait another couple weeks for the battery to ship.

And, you can get the same cardio per unit of time (if you want) on an ebike as a regular bike. You just go faster, therefore further. And since you have a bit more speed, and you aren't required to do a major workout on every trip (so you don't have to change into cycling clothes), you end up using the ebike for a lot more trips -- therefore getting more exercise overall.

In my case, I have a 25 mile commute -- no way to make it in time on a regular bike. But an ebike makes it no problem. And I still get a decent amount of exercise (basically the difference between going for a very long walk vs running a sprint, so a different type of exercise), and on the weekends I give it my all (and just rack up more miles).

I see a ton of these every time I'm out on my bike commuting here in the valley. My first reaction is "how the eff is that guy riding so fast" then I realize he MUST have an assist because it's a more casual looking rider on a more upright style bike, he's still pedaling but just FLYING.

Ehhh, unless you see the motor, he might just be pounding along with his own two legs. I ride year round so I'm in pretty good shape for biking but I still occasionally get smoked (uphill) by some guy on a MTB with a seat that's too low and sporting a rusty orange chain.

I commute via ebike 6 miles round trip. I still sweat. The main advantage for me is that I have much better acceleration, can cruise at 20mph without a ton of effort, and can climb the steep hill I live on at 10-15mph instead of 5mph.

I like that I can use leg power and get some exercise on the way to work in the morning, then in the evening I can just cruise home on battery power and not get sweaty.

If you're male, consider that long-term bike riding can cause infertility, erectile dysfunction, and prostate problems esp. depending on the saddle you use.

The science still doesn't seem clear - for example, a recent study in the UK (presumably the largest ever) showed no evidence of increased infertility: http://online.liebertpub.com/doi/pdf/10.1089/jomh.2014.0012

That's if he uses a saddle.

What's the alternative? Standing on the pedals? Or are there other styles of seat, not covered by the word "saddle"?

There are "noseless" saddles and saddles with a channel down the middle that may help protect the sensitive bits. http://www.thebirdwheel.com/noseless-saddles-tested-updated

But my biased opinion is buy a recumbent! Fewer back, neck, and nether region issues, plus, they have comfy seats! http://www.bacchettabikes.com/recumbent-bikes/

VERY comfy seats! http://www.hpvelotechnik.com/produkte/scorpion_plus20/index_...

A long wheelbase (crank behind the front wheel) and a more upright riding position is perfect in city traffic. On my commuter, my eye level is about even with drivers in crossover vehicles.

OK, that's closer to what I thought. I was kind of thrown off by the previous comment, which I read as implying "there are things besides 'saddles' that you can use".