Civ for Cultural Diversity!
Another new feature in Warlords is the inclusion of unique buildings for all the civilizations. Every unique building replaces some regular building for a specific civ, and comes with an extra bonus. These bonuses vary quite notably in strength.
Unique buildings do not create extra strategic depth, seeing how they replace some buildings – hence, there's not the option of building one or the other, it's just that one option gets swapped for another. The feature, does, though add some extra flavour to the game and it helps to make each civilization feel more unique.
Unique buildings, as far as their actual usefulness goes, are quite diverse. As you would expect, the earlier unique buildings are more useful, simply because they're going to have that much more impact. The Russian Research Institute, for example, gives 2 free scientists, which is a very good bonus, but seeing how the building replaces Laboratory, it just becomes something to extend your lead.
Several unique buildings have very interesting effect. In this regard, my favourites would be the Viking Trading Post (replacing Lighthouses, free Navigation I to sea units), the Spanish Citadel (replacing Castles for +2 XP to siege units) and the Roman Forum (replacing Markets, +25% Great People birth rates). An honourable mention goes to the Mali Mint, which is a Forge that also gives +10% gold. Coupled with the Financial trait, it makes Mali the best money civ in the game.
My overall impression of the unique buildings is that it's a good flavour addition that will make it easier for some people to decide on their favourite civ, and just add more uniqueness all around.
Speaking of unique things, the new Unique Units also deserve a mention. They are, thankfully, for the most part rather interesting strategically. Ottoman Janissaries can be a very good weapon in single player games. Being Musketmen with a 25% bonus vs. archery, cavalry and melee units, you can do Big Bad Things (TM) to AI civs if you can manage to get Janissaries before the AIs get Gunpowder. An Ottoman beeline for Gunpowder has the potential to be one of the strongest strategies against the AI, which will be protecting its cities with units that are at a disadvantage against the Janissary.
The Korean Hwacha is a Catapult with a 50% bonus against melee units, which makes it, briefly, a good field unit. Still very vulnerable to mounted units, the Hwacha compares favourably to all three melee units of Classical age.
Korea is a very powerful civ in the right hands. It has a pretty unique quality of being able to do both a religious building game, and a powerful early assault. Starting with Mysticism gives you a good chance to found a religion, and starting with Mining means access to Bronze Working earlier, which, in turn, reveals Copper and allows an attack immediately. Wang Kon's Financial trait clearly helps any and all building, whereas the Protective trait is very useful for an early choke, and makes fighting slightly easier. Add to that a Catapult replacement that can hold its own in the field against everything except Horse Archers, and you have a civilization that can do some early conquest while having a religion and a solid economy.
Finally, I would like to give credit to the Zulu Impi as the ultimate pillager. A 2 move Spearman that ignores terrain movement cost, it's a pillager's dream. Horse units are not effective vs. the Impi, and it's not too easy to build Axemen when your metals are probably the first pillaging target. Here I am glad t say that the AI understands the power of Impi when used as pillagers, and will not hesitate to show that.