The first thing I noticed on the Character pages is the lack of Precision Shots/Strikes, a quick flick to the special rules section tells me that the rule still exists, but there is nothing that indicates Characters have it. Never mind, I always forgot that rule anyway! Everything else is the same, even the Look out Sir roll...
Now to look at Challenges. The first sections are all copy and paste until you get to the Fighting paragraph, where it says that models and Characters that move to satisfy the challenge are unable to pile in at their initiative step. Any excess wounds after a Character is slain are now allocated to the next nearest model! The morale support rule has gone and other models can now attack the enemy in a challenge once they have slain the rest of the models in the unit.
That's about it, next up, Battlefield Terrain