It's a lot like Age of Empires 2, less technologies, better graphics, a wild west story line, easy to learn to play.
The game is not hard even at highest difficulty, and has a few bugs with whom you can cheat the AI players, but only for a limited time.
It has a wild west kinda feeeling. It works great on win 98, XP, Vista, 7.
The expansion pack doesn't work good in Vista and Win 7 meaning that you have to use a 800 by 600 screen resolution, which makes playing very hard.
You value every unit in the game, that is nice.
Unlike AOE 2, the units are easy to control, organise, everything has a nice flow, and every unit is different.
Also unit's damage depend a little on morale, wich is higher when the comandant is alive and closer.
HInt for online play:
In the expansion pack the faction The Mexicans has an edge, if you build carages and fill them with canons you are almost invincible.