It depends on your situation. ; I wouldn't recommend one in a big, tightly-packed crowd, but otherwise it's not too bad. ; I found that I tended to keep my right hand on the camera when I was walking around to keep it from bouncing around too much. ; I even used it with a 70-200 zoom; connecting to the tripod socket on the lens meant it hung perfectly balanced at my side.
If you get a chance to try one out, do so. ; They're kind of expensive to just buy on a whim.