4/5 for me.
The combat is done right and is a vast improvement from Civ 4 (would be nice to see counters to units in place without over complicating things... for example, swords are better than axes in attacking
) but the AI seems lacking. Of course, the Civ AI has always been fairly bad, but that doesn't excuse some of the things that happens with the AI.
For example, the early game AI is terribad in Civ Rev. They don't seem to have much of a strategy. They also have personalities (do they even have them?) that conflict with what the civ is built for. For example, The Mongols don't seem to take out Barbarian cities or spark combat, Ghandi is usually the first to declare war... and some other odd things.
There are some other quips I have with the game as well. The lack of city upkeep as well as a lack of unit upkeep means that you can win by ICS with every civ without much thought. There isn't a real need to build AMAZING cities. Just go for an early Republic, churn out tons of cities, and build nothing but military units while teching straight for military units. You can win any kind of game like this without issue due to the number of 'good' cities you'll have taken over.
The lack of civics means there's less to worry about, but this is one area I wish was equal in Civ 4.
Everything else I love. The combat is a vast vast improvement, the speed is perfect, and the viability of cultural, tech, and economic victories is a nice change. Also, the different ways you can go about each victory (compared to Civ 4 where each victory was a pretty rigid path) is something I wish Civ 4 had.
Speaking of Civ 4, I hate cultural victories in that game. Hate. Absolutely hate.