IME yes, but it depends on what we're talking about. On a long (10 minutes+) climb, I'll stand from time to time just to break things up. I don't work that much harder, if at all, but changing the position and muscles used is a bit refreshing and seems to make the climb easier. Even if it doesn't actually make a difference, it seems to, and that's enough to make me feel better.

On very long climbs, I'll also alternate long intervals of grinding along with intervals of launching an attack, say to the phone pole up the road, then settle in again. Like with standing, I don't know if it makes a difference, but it does help get me to the top sooner, and there's a bit of psychological boost and it makes it seem that I'm getting someplace faster.