I've been playing (properly) for ten years. When I first picked up a club it just felt very un-natural to hold it any other way than cack-handed - and I still play cack-handed.

I find it gives me no dis-advantage in distance - I can hit the ball straight and far. I do find that I get less elevation on the ball than most, which may be due to a more closed club face at impact (due to the cack-handedness).

I've often thought about changing - mostly due to comments from other golfers (you can't play like that!.... you should fix that grip etc...) but it suits me, I'm comfortable with it, and it works.