Great game. Lirat in countless hours, it becomes very difficult on hardest difficulty level. AI is based on the difficulty level you set, ie if you are running on easy / normal you win battles and campaign relatively easy. It is on the harder levels as the game is flourishing.
Incidentally, did the game quite well on my old PC (P4 3.6 x2, HD4670). Installs right now through Steam on my new, överclockade and phenomenal computer (see Battlefield PC I built). That the game laggy, I have not understood at all. Charging times if one Quick Save / Quick Load: s is rather dull, but they are quite unreal they anyway, so I use me. What pulls down the score of the lag for many other players, AI, total oimperialism on lower difficulty levels, and that the game could look better on campaignmap.
Supporting dualmonitors were not entirely wrong, either, but there are few games that do (Eyefinity to the rescue!). Undoubtedly the best turn-based strategy game I've driven, above all, the excellent Total War games (have almost all: D). Total War FTW!