I agree, it is pretty insane how much it helps (although when thinking logically, it makes perfect sense). My rule of thumb lately has been that any hole under 400 yards, I tee off with a 4 iron; that is unless the hole is wide open. If my driver is hot, I ride it out and overule this. I can usually go 4 iron, 8 iron into a 400 yarder, so it makes perfect sense to me...the only downfall is when I miss the 4 off the tee and leave myself a long way in.
I've heard rumors that you can play the game from the fairways but I prefer, so it would seem, to play my second and perhaps third shot from the trees. Clearly the main reason they designed the 4 iron.
Sounds like you have had a few good rounds as of late. Were the winds down today?