RIT does work very well in my view, but only if it is utalized properly. You need to have Firefighters that are trained and experienced in Rapid intervention procedures, because if someone does get trapped and a two or three man RIT goes in and gets lost or trapped theselves you just elevated the problem.
In my nine years in the fire service I have only seen a RIT used thankfully on only five occasions. They were successful in each of the rescues. Unfortunatly on one of the occasions the Lt. leading the operation ended up carring out the firefighter and the firefighter that went in with him. So, yes, RITs are a very efective tool to have at a fire scene. Only when used in the propper manner!