Was in the same situation as you, and picked up the 360 version. Love it tons. It's not the prettiest game, but it's not as bad as some people say, and it's very playable.
My only real complaint is the lack of "hotbar" space. You can access the abilities you don't have hot keyed by bring up a time stopping radial menu and it works well enough, but I tended to forget all of the abilities I had access to and keeping tabs on their cooldown timers was rough for the ones not hot keyed.
Tactics settings for your AI companions are very important
- They're kind of a pain to set up given the menu system and not always completely clear skill descriptions and tactic limitations, but they are absolutely necessary particularly if you use any mage characters (and you will).
Having at least a working knowledge of how combat in an MMO works helps
- DA:O combat is very MMOish, right down to tanking and party class compatibility. You don't really need it going in, but the game will kick you butt pretty quickly if you don't at least pick it up along the way
If you have any specific questions, ask away. Don't be afraid to pick the game up on a console though, it's well worth it and doesn't suffer anywhere near as badly from the transition as some people say.