Which are the improvements on single player in Mount & Blade: Warband?

I liked Mount & Blade and I would like to known which are the improvements on the single player in Warband about gameplay, graphics, etc.. I am not really interested in multiplayer.

Here's a list of some changes that I've noticed

• A new faction was added, the Sarranid Sultunate.
• The map and faction positions have changed.
• There are new political options, for example
  • If you create your own faction, you have the option of recruiting enemy lords
  • Marriage, which works differently if you are a male or female.
• Combat has changed slightly. However, it is difficult to notice unless compared side-to-side. This affects things such as swinging animations and projectile accuracy.
  • Individual arrows, bolts, and throwing weapons can now be picked up off the environment if they miss the enemy.
  • It is more difficult to hit enemies from horseback.
  • In my opinion, the combat is worse. Swinging your weapon is no longer as quick or as intuitive as the original. They probably made these changes to balance the multiplayer mode.
• The graphics are now better, though still nowhere near that of games with large development costs.
• There is support for custom single player battles, where you can choose the two factions and Cavalry/Infantry/Archer ratios as well as the map and game type (battle and siege).

As a side note, the multiplayer mode is quite fun and I suggest you try it at least once.

The biggest changes were to the politics system within each faction, namely:

• Honor has a larger impact on how others perceive you
• If you are friends with a lord from another faction, you may avoid combat with them as a "favor" and potentially persuade them to join your faction, whether you have started that faction or not.
• Lords have individual tastes and goals, and will start to become rivals of other lords. When you attempt to persuade a lord to switch sides, for example, he will make the decision based on which faction is more powerful, what claim to the throne your faction leader has, what personality the majority of the lords in each faction has (i.e. honorable lords don't like dishonorable ones), and his own friendship with your character. Some lords will change sides when they finally grow sick of their own faction (e.g. fallen out of favor with their king).
• Wars between factions are still affected by random events, but do not start and stop with no warning whatsoever. You can determine how a faction feels towards another by asking Guild Masters.
• The player can now become the Marshal somewhat readily, and control the 'banding' of lords near them by talking one of the companions or lords. Asking other lords to perform tasks is easier than in the original game, but a lord will dislike you if things do not turn out well.

As Aviv mentioned, a new faction (Sarranids) were added. They're strongest at heavy cavalry and foot archers.

Wars can still be frustrating in the early-game, but when you become the Marshal things get somewhat easier.