Despite what I has said previously, I did break down and buy it.
Pros: The AI is a little smarter in terms of Combat (although they will still send a single transport and declare war)
Cons: Several people, myself included CANNOT play the game if the Ottomans are involved. There is a problem with Mehmeds Leaderhead.
All in all, they didn't add much, the Great Generals I think are the biggest gain the game got. But if you don't have the money wait for the inevitable second XP, because this one didn't change enough to be worth buying. If you love scenarios however, the game is a must get.
Installing Warlords DOES NOT prohibit you from playing Vanilla CIV.