Has anyone moved a single forum from one board into another new board (along with a copy of users) before and had success? Was it easy, or messy?

My guess is it's messy.... you need to incriment all the post numbers by a set number so that they don't "step on" existing posts numbers, yet all match up.

Likewise with users.

If you are talking about moving a single forum into a clean install I can see that as doable. Just restore the whole board and trim off the extra forums and catagories. But if you are talking about taking an exsisiting forum and moving it into a an exsisting community, then yeah, messy like Josh said.