I agree. A hex map would be the greatest improvement of Civ since, well, ahem, how can I end this without being rude? :-) Since the first original Sid Meier's Civ. At least the greatest topological improvment.
Another map related issue is this: I would like to have an option to play in 2D-mode, i.e. without the semi-3D view. Just like in Sid's original Civ. This will be especially handy when you play on a hex map. /Chrisp