From what I read before I got him, I assumed he would stay around the bottom sifting sand, but that isn't the case...
He constantly has a plume of sand behind him, and he can't stand to see a patch of detrius in the tank. He's a very friendly free-swimmer, and uses the whole bottom 3/4 of the tank to swim around in...he's very entertaining and hardworking.
That said, I would probably have a problem with him if I had a lot of corals in the bottom third of the tank. He does spew sand over a lot of the tank, and can be a little obsessed with taking all the sand out from underneath the rocks. Sometimes he'll get a big mouthful of sand and cruise over the rocks like a crop duster, which can be a little annoying. At first I had the turkey baster out a lot, but I stopped fighting it.
IMO though, he's a great addition to my tank.