I think of it as belonging to people in my own generation. Which isn't a bad thing, IMO. But yeah, dad name, I guess.
I never liked it on my peers. The Dug sound is clunky to me. Makes me think of hyper guys like the Douglas I knew in elementary school, and of Michael Douglas. Still, I don't disapprove of it as a baby name now. It's a decent name, and maturity doesn't hurt it. I don't like nn Doug, though.
I'd probably be more inclined to like Dougal instead of Douglas.