We've had some Trek Ride+ electric assist bikes at the shop for awhile now and while I've done a few test rides around the block I've not taken it for an actual ride, until now.
This isn't a moped, there is no throttle. You have to be pedaling for the assist to be active: stop pedaling, no assistance. Even still, I didn't break a sweat on my 5 mile commute this morning. I was a bit let down with the 16-17mph top speed but the thing is that the speed was consistent. Where you really felt the drive kick in was at lights. Taking off you have a quick burst of help that gets you up to speed and from there all you have to do is make sure the pedals are moving.
So check my outfit: pants, undershirt, tucked-in polo shirt. This was the "Casual Friday" dress when I worked at a law firm so I know plenty of people dress like this or similar every work day. With a bike like this, "sweaty and smelly" is no longer an excuse for not riding to work.