It definitely works better on a dude's larger wrist than my girlfriend's. That said, she still loves it and wears it all the time. She especially likes it for running /w Nike+ and headphones.
So in a word, no the nano isn't too large if you're cool with large watches in general. The weight is fine. The band is pretty cool, I kind of get annoyed with the little lynchpin sticking up funny because of the shape of the arms.. but everything is pretty awesome considering.
The materials used seem pretty solid, I've abused it pretty hard and like I said before it goes running.
So yeah. I'd recommend it.