Summary

This review was originally posted on VersionTracker.com.
If you are considering buying Civ 4 Warlords, carefully check the system requirements
to have smooth play, ensure at least 900 MB of ram extra for Civ 4 to run
(people with 1 GB of ram will notice pauses as the system will have to use virtual memory, this is true of windows as well)

I have run into some bugs with multiplayer (I mostly just play with one other person against the AI, so can not give feedback on 3+ person games) especially Out of Sync errors
with limited testing hardware available, not sure if it is a mac/windows problem specifically, but it doesn't happen every game (seems to depend on how many units are actively being moved by the computer in a round, which means it can happen late in games when wars are going on)
I've also had some very rare crashes of the game (also happened in the original Civ 4), fortunately in multiplayer, the other player can just save, or wait for you to reconnect, no lost turns.

To play over internet, if the host has a router, you do need to open several ports in the routers firewall to allow things to work correctly (these are documented several places, I found them easily in a google search, www.portforward.com for router instructions)

now for the real review:

Good improvements to the war & battle sections of the game, the AI's are noticably more aggressive than in the original Civilization 4. If you wanted a more aggressive Civ 4 experience, pick up this expansion.

more countries, more AI's, more units, addition of Vassals
the single player has totally new types of gameplay
there are many 3rd party maps, new units and mods available from places like civfanantics.com (so far everything I've tried has worked without any issues specific to the mac version)

If you have liked civilization in the past, and have a relatively new computer with plenty of ram (I have 4 GB in this MacPro) I highly recommend it, your spare time won't be spare any more.

now that my inner warlord is satisfied, I can't wait for "Beyond the Sword" to be released for Mac.