Just out of interest, which infantry units were running as fast which cavalry units? What type of town where you assaulting with who and against which army?

Personally I think the battles in this game are bit slow to start and over too quickly, but that could just be me.

The assaults on towns can be fantastically easy when attacking a little fort or an exercise in pain if attacking the Epic scale walls.

I think it could just be that expectations were built too high, after all, the game does [I]look[I] fantastic and if any part of the game doesn't reach such sparly standards then it really shows up. I have to say that I have never seen the AI do the things you say : running backwards and forwards across a bridge under arrow fire seems just plain silly. In the BI game I have played I have seen the ememy start to attack me and draw back to lure me across the bridge, walk its archer units to the edge of the river and swim some cavalry across at the extreme edges of the river to try and flank me.

Sounds like you may need to tell your game off and buck it's ideas up :)