Please, please don't misunderstand me, ladies and gents.
I'm not saying that shafts are worthless, that any piece of steel or graphite will do - far from it. I'm saying that you need to find a head that will work first, then find a shaft that complements it. If you play in lush conditions, butter-knife blades are not your friend. If you play in dry, firm conditions, wide sole irons are a wide open invitation to the Bladies - you know, the award show where the longest bladed shot wins. In drivers it gets even better... for the majority, I'll stick you in some 4° true to spec head and giggle. For the higher swing speed players, I'll put you in a 16°, 2° closed head and watch you hit 220 yard ballooners.
:O
But as GB points out, once you have a head that works, you need to find a complementary shaft. But his line "I had to slow my swing to get it to work" proves my point - wrong shaft, still got decent results. Not best, not optimal, but playable.