"A mixed blessing"
If you have an ATI video card, expect some serious problem getting this game to run at all. Major issues.
The gameplay follows the old precepts, but it's been done over in a good and refreshing way.
Diplomacy is much better than before.
You have many options on how you govern your empire, in a way similar to what you can do, policy-wise, in Alpha Centauri.
Units get experience and promotions and you can customize them as you see fit - for city defence, for fighting in woods, for attacking certain types of units. You can get units started with bonus experience - the possibilities are plentiful.
I like this one much better than Civ3, not at least because the annoying "corruption" is gone, and the micromanagement is reduced to a happy medium. You pay maintenance on cities, not buildings: build too many cities and you can bankrupt yourself!
Alas, 3/4 of the way through a game things get very unstable. Crashes which never seem to happen in the early game become a regular occurence. The demands the game places on the hardware and operating system are ridiculous, considering it's a turn based strategy game. What did they have to use a bleeding edge 3d engine for - it breaks the game. I do hope they will patch the problems - I expect after another few crashes I will shelve the game indefinitely until it gets fixed. Loading times are insane (minutes) and two or three crashes in an hour are a killer.
In the meantime, until they fix it, I would recommend you hang on to your dollars unless you are keen on lots of frustration.
5 out of 5 stars for gameplay, only 1 star for technical issues, sadly.