@Gercog: New units, better graphics, almost completely new AI, some gameplay stuff, bugfixes, etc. ;)
Here's a quick preview of a sicily campaign of mine, turn 269:
http://i.imgur.com/CGKQN1E.jpg
Im progressing really slow. I had controlled some byzantine areas, but lost them when they struck back as i wasnt as powerful as I am now. I think I finally wrote an AI which is capable of defending properly. When I checked, they really split up their troops to leave no border uncontrolled.
I then started to conquer italy, which took me about 100 turns I guess. So around turn 200 I started war with france, of which I just gained arles but cant really move further for now.
Vassallages work for up to 3 settlements now. F.E. england was a vassal of france for a long time, they just now started war again (since they noticed im beating up france).
There's a new event cancelling all diplomatic relationships for small factions when a new leader get on the throne, since vassallages up to this point were a dead end where they couldnt invade anything anymore. This makes things much more dynamic.
Also naval invasions work better. F.E. When the HRE controlled burgundy, they actually captured mallorca. The island then went back and forth between aragon, hre and the almoravids.
There's a global reputation system now. It's basically there to prevent rushes. So if you capture a settlement (or do anything else agressive/bad), you'll get a negative reputation. Obviously the harder you punish the settlement, the worse your reputation gets. With time, your reputation normalises to a certain level. If your reputation gets low enough, basically everyone will attack you. If it gets high, there's less chance for you te be attacked. So the game motivates you to play slow more than to blitz everything around you as fast as possible.