Only once, in maybe 300 battles of MTW2 so far, has the enemy general made the same mistake he made in 99% of battles in RTW.. that is, charge my army unsupported, getting easily enveloped+killed, and giving a huge morale hit to his men. It was fun for a while but made the fights too easy. The general, and cavalry as a whole, are also smarter about being lured away, and try to stick with the infantry so that they can be more effective.
I miss something about RTW though. When an army routs in MTW2, your loud accented sycophant says "The enemy flee like a pack of goats!" I never thought I'd say this (as I once hated it) but what happened to the rest of that sentence!! (Hunt them! Goats make for good eating!)