I don't and it hasn't been a problem. But something you never want to do is have the bath exhaust fan turned on when you flush. It will pull the odor right into your face, especially if there are no open windows or doors in your rv.
But if you have a sensitive nose or the waste plumbing isn't sealed tightly, it may be something you'd want to use. I'd say if you have a problem with odors, try some to find out if it helps.