The demo is restricted to the tutorial, which is based on the smallest scenario available, and the Yorktown scenario, which is very focused in essence (the actions will take place on 6 regions roughly).
Now things are differents with the campaigns. To start by the begining, they are totally differents: the French Indian War and the War of Independence have few things in common, to say the least, and this will impact greatly the gameplay. Even for a given campaign, both side play totally different:
in the FIW, the French rely on good leaders and mobiles units (indians). The English on regular infantry, coming more and more. They must bid there time. In the AWI, the American try to stay alive early, while his militias are poping-up (and you won't know where they will arrive!) and wait for the French to give them a hand. The English are strong initially, even stronger in 76-77, and then that's about it: if they fail to beat significatively the Americans, they are toasted in the later part of the war.
Just by playing the 2 campaigns, once for each side, should give you enough fun and playings hours to repay largely the bucks invested in the game, but I'm partial. If players want to give their opinion, they are welcome.
As for variability, the militias (rebels and loyalists) are randomised each games. The French entry is very variable, and will depends of your success (or failures). You can have them in 77, or not have them and its 79! The main english renforcements can arrive in Halifax, Quebec, or the British West Indies, etc. The AI will play totally different depending on where she get reinforcements, and what you will do (she is very flexible

).
To sum up: at least 100+ gaming hours where things will be differents. AI is reactive & agressive, game is very stable. The subject is seldom the focus of PC games. Historical research has been extensive. You can PBEM a live opponent after having played the 15 scenarios (and a new big scenario is being made by Philippe Thibaut).
ok enough for me. I hope players will give their input!