CVG has an interesting preview of combat in Warhammer Online:

War never changes. Literally in MMOs, as regardless of how bitter a conflict is it all whittles down to a few games of Capture the Flag with the eventual putting aside of differences to save the world. However, in the gritty Warhammer World, everything is to play for - every zone, every territory -as from Rank 1 onwards, you're very much at war, the enemy is near you, and you've got the chance to fight for your realm....

This kind of accessible, realm-driven combat is an example of EA Mythic's main goal for AOR - NPC and player combat that flows together naturally, culminating in a siege of the main cities.

This will be, the developers tout, a huge, 100-200 person battle against players and NPCs, that finishes with a final scrap against either one of the leaders, such as Tchar'Zanek or Emperor Karl Franz. You'll be able to burn the town to the ground, while murdering the populace and looting for a day, real time, as well as exploring the city's unlocked dungeons, special vendors, and capturing the defeated leaders and placing them in stocks in your capital.
You can read the rest here.

I love the idea of being able to pillage enemy cities! If they can make this work, WAR will be an awesome game.

There's also a good beta video here.

Lastly, Gamespot UK has a good interview with one of the devs here.