I've withheld as "punishment" once or twice and while it might seem slightly immature I don't feel Immature for doing it. I actually find that thought VERY offensive. I tell him WHY I'm doing it, we're perfectly clear on that and we have no trouble communicating, but I've still done it.
On the opposite end I don't withhold when I want something, but rather I'll offer sex. He would do the things I'm asking him to do regardless of sex, but sometimes it's fun to add a little incentive. It gives us both something to anticipate and usually gets whatever he's doing done a whole lot faster.
It works the other way around too, where he's the one offering or withholding. I don't find sex to be the be all or end all of a relationship. If you really love someone I think you can always find a way to work through any issues in or out of the bedroom.