We still have a sound monitor in my almost 5 year olds room....we are very heavy sleepers and all sleep with our bedroom doors shut. Our rooms are all upstairs but the way our house is setup, the boys are on the other side of the house with a closet and bathroom seperating our walls. I'm sure we could take it out of DS1s room but on nights he's not feeling well or sick, it really comes in handy. There have been some nights where he's gotten sick and I wouldn't have known if I hadn't had the monitor on and heard him. We'll probably take it out of his room soon.....maybe I'll grab it out of there today.
I will say that when he was about 3 and we switched him to a twin bed from a crib, the video monitor came in handy. We were able to see if he was staying in bed and could remind him to hop back in bed with the 2-way talk feature. I don't see us getting rid of DS2's monitor until he is sleeping in a big bed consistently.