Except as was previously mentioned, if the room has carpet, it doesn't work very well. Also, if you're playing in leagues, even with a hard floor, being able to hear that over the sounds of all the people on all the teams playing is pretty hard.
I myself save the "good shot" saying for when it was a really good shot, ie. something they normally wouldn't have made. I say it to my teammates especially to give them a confidence boost. They won't get that boost if they can't hear me tapping my cue on carpet while 20 people within hearing distance are all talking.
Brian