I think that M2TW was okay. Not good, not bad, just okay. The graphics are way better than in RTW, and the varied apperance of soldiers add to the feeling, but there are a lot of bugs that ruin everything. Without patches, the battle AI was worthless. Sometimes, an enemy army walks up to you and stops in front of your army.
Then they wait.

And wait.

And wait.

Until the time is up, or you have shot them all dead with your archers.
With the patches, it got better, but still, the battle AI was, in my opinion, better in RTW.
Kingdoms helped a bit, but there is still a long way to go to perfection. (Okay, perfection might be pushing it a bit to far, but you get my point.)
Campaign AI, on the other hand, does reasonably well. They use naval landings, and the classical "siege, no siege, siege, no siege"-problem, is almost nonexistent.
So all in all, M2TW is... adequate.