First thing to know is Big Changes Happened.

How individuals deals with change will be the mark of how they deal with The Big Changes.

There are 2 massive changes: Trait Trees and Big Battles.

Trait Trees

The sky is not falling but you are going to get a big WHOA when you first really look at them.

You will be altering some of how you currently play. This is a fact. You won't do what you do today the way you do it today. This is because of the way skills and abilities have been parsed/altered in the trees and some items have been removed.

You will be able to do the content old and new. If you can do the content now, you can do it when HD comes around but you will do it differently. Your class trees will shift your skill sets and you do have to make choices. You won't be able to Have It All and Have It Now. You can have access to all of it if you shift from one tree build to another.

Shifting to a new tree is not hard or difficult. You can prebuild quite a few and buy slots for more. To shift you will need to be Out Of Combat.

ex:
You can be in Healing Mode, shift to DSP mode, shift to Healing mode but the shifts have be done Out of Combat. Working in groups will be a bit more of challenge only in that those members who are trigger happy will place a group into combat before they can get a new build. This requires only an extra short pause and few clicks. Just like currently there are some things you cannot do in combat (eat food, scrolls) you will have to add in: Shift Trait Trees to the list.

Big Battles

These will be both interesting and confusing. It's an entirely new system. It has its own rewards (medals) and there are a number of versions to try out. The Big Battle Tutorial quest giver is located at the Boar Fountain (beta). I recommend everyone take the tutorial. The equipment is not hard to use but if you are trying to figure it out on-the-fly it's going to make your experience tilt some.


Overall

One thing to remember: much of what happened in Helms Deep was a retreat, not an advance. You can retreat from the challenge or learn to crank the ballista and fire the catapults. When you see the orcs coming over the walls in waves after waves... will you Run or will you Stand and Fight?