A man named Steve once said to me the following:
"I haven't touched a circuit board since 1986... and if the boss knew that, I wouldn't be working here!"
Eventually, Steve was no longer working at the company.
The thing about using hexagons instead of squares realtes to that because it would be something so... different, that it may take trouble getting used to. People who are used to the square array, or have not played on a hex grid in such a long time, may have so much difficulty in using it that they'll leave the Civ game, which would be a terrible thing.
Perhaps they could make it an option in for a future release or expansion pack, as it's kind of late to revamp something of that magnitude (I've been developing a city-building game in VB so I know what goes into it). I would definitely like to try out the hexagons, but I probably would prefer to stick with squares for a majority of the time.
The 1.5-tile rule may confuse players, although I think it's a good idea, having 1 movement point expended when moving on a diagonal probably doesn't affect the gameplay all that much. I personally think that counting it as 1.5 may detract from ti further. If you go to move a 2+ movable unit, and you only have 0.5 points left, people may become frustrated that they can't move the diagonal.
So I think we should keep it as squares with movement costs of one (like previous Civs), but perhaps allow the option of a hex grid in the future.