Just wondering if anyone else has had the same trouble. I run M&B maxed out, with about 200 men battle size, and the game runs like a gem. 9 times out of ten I get no lag at all, but if I mess around and get into a battle in one of those 'hill/mountain' terrains, the game drops to like 3 FPS. You know, the terrain where you can't easily use a horse, and everything looks like crap because infantry is flying up and down cliff-sides.
I've tried disabling a number of things, but nothing seems to help. If it was my choice I'd just disable that type of battle field and be done with it. Maybe the zonky terrain is causing huge pathfinding lag?