Yes, water does indeed make a difference, hence my first posting to this tangled thread. When Devenish Brewery moved their brewing from Weymouth to some where in Devon, the difference was noticeable immediately. Most of Dorset is chalk, which acts as one of the best natural filters in the world. Devon is getting towards sandstone, which filters about as well as a pound of sugar. In the drought in 1976, Dorset was one of the few counties that didn't actually run out of water, due to the subterranean stores of water under the chalk. Devon was reduced to standpipes and rationing long before much of the rest of the county. Guiness brewed using water from the Liffey really does taste different than that brewed elsewhere(or so the SO tells me, I can't stomach the stuff...).

LTS