I partially agree. I think the single largest improvement to my game was the investment in lessons. I signed up with GolfGalaxy and their local pro here in Edmond, OK. It cost me $130 for three video taped lessons that were then e-mailed to me. I have played for 16 years in the low 100's.
I had the worst push slice and I was too stubborn and constantly tried to fix it myself -- which consisted of me almost facing dead left to hit somewhat straight.
In the first lesson he recognized that I had a weak grip and made a couple of other small tweaks that immediately started me hitting dead straight with a slight draw.
I don't get into all the golf gadgets but I try to keep an open mind about the mechanics of my game. If I start having old items pop into my game I go back and watch my video lessons.