It's not as much about what it does, it's how far it does it and how it gets there. Learn the punch shot to fill in yardage gaps in your coverage like D pointed out. I carried 4 wedges up to Legend and had 20 different coverages where you need it most, just with the wedges. The punch shot made that work along with the other shots.
Learn the shot by the distance you can cover with it. It isn't as affected by wind as much, is a good out of any kind of rough (once you learn the shot) and on courses without trees you can get some really nice long rolls. Good to use when the wind is howling. 3W punch out of 40-50 is an excellent recovery shot.
A retired player once told me over 3 years ago, when the Satin64 was the bomb, that the punch with it was the most valuable shot he had. I was so new I'd never even considered it. Needless to say, today it's one of my favorite shots.
Incidentally, that player was AvatarLee. :-)