That is a pretty sick move to make it 3d :P
You have a good point about the unresponsiveness, but stating that in clear text to the user would be a quick fix for that tho. I mean, nobody likes to wait, but if you feel you know why you are waiting, most people are a lot more OK with it. Might be moot if the 3d method is that much better at drawing.
Hey, totally unrelated to this, but do you plan on adding rivers? Either through the cities or around the outskirts? With most cities in the real world springing up around them, I would think it a pretty good addition to this excellent generator.