OK... so it appears that the majority believe there is a difference, even if it is just a subtle difference...
That leads me to ask a few more questions then...
1) Why do high-end restaurants, that can afford the best of "setups", grill over gas?
2) I have done my fair share of charcoal grilling over the years... and I get just as many "this food is great" comments whether I cook on gas or charcoal... in fact my last steak cook was done over gas, and was probably some of the best tasting steak I have ever done.
3) When grilling w/ high heat... it seems everyone claims they can taste a touch of smoke... I don't think that smokey taste if coming from fuel source, but rather fat dripping?? Not sure, but I think. If I am correct, I get the SAME smoky taste using Grill Grates on my Genesis.