Have only just bougth civ4, and not being near my computer for a few days I've been limited to reading the manual.

Unit upgrades look interesting, far more reason to pay close attention to the military! However, I was wondering how intelligently the AI uses these upgrades. Will they simply go combat I, combat II, etc., or am I going to have to prepare for a more complex military threat?:)

first, don't think upgrades and promotions are the same.
you're talking about promotions.
And yes, the AIs use more complex (although not necessarily wise) promotion sets.

Ah, yes. I did mean promotions rather than upgrades (and bought instead of bouhgt). Thanks for the answer, it's nice to know the AI has some variety. As for wise, well that would be too much to expect.