AOE 3: the Warchiefs expansion seemed at first glance a tad pricey: an expansion pack that is as expensive as the original game? But once you get into it, you realize it alters the original game, and the way its played, enough to more than justify its cost.
First off, the single player campaign is as lengthy as AOE 3. Its an almost-as-engrossing storyline, with almost-as-interesting characters. The missions have been creatively remixed with never before seen win conditions. Its a blast.
Second, and most importantly, the skirmishes are turned upside down and inside out, in a GREAT way. The addition of the 3 new nations: Iroquois, Sioux, and Aztec totally changes the game. They are obviously not European, and therefore do not build fortresses, or advance in tech the same way. They are highly mobile, with all new classes and weapons, and town design is radically different. The "Warchiefs" (see Explorer) are now capable of becoming an army in their own right: they can "charm" treasure guardians to become theirs, and add buffs to surrounding units. They also can be upgraded to become formidable warriors with hitpoints up to 2000. Gone are the days of listening to your explorer moaning because an alligator killed him over 30 wood!
The native societies advance differently too: ceremonial fires provide an array of buffs to your town, warriors, production, etc, which allow you to really experiment with how to win a map. For example, the Sioux do not need to build any houses: they start with 200 pop...teepees can be built simply to give defenders a bonus! Iroquois huts have an attack!
Added to this are 3 other fun changes: there is a new victory condition - trade monopoly. If you control 2/3 of the trading posts on a map, you can start a countdown timer to win...if you can hold on to your trading posts! Another is the addition of NEW units to your existing European armies that revitalize playing them. Lastly, and most significantly, as a European nation, you can declare "Revolution:" break away from your home country, and place your entire society on a War footing, producing militia instead of settlers, new weapons, and as many fortresses as you can handle!
Warchiefs is slightly more graphics-heavy than the original, altho it plays perfect on my macbook with 2 GB's of Ram and the GMA 950 integrated graphics card.
All in all, it is worth the price, and will get you back into your beloved AOE 3 for months to come.