It's not a fantastic game like Origins was. It has a lot of flaws. Don't expect to be blown away. (Also don't necessarily build your characters the way you would in Origins- the battle system's fairly different.)
All by itself, if you weren't a fan of DA:O to begin with, I'd say probably avoid it. But since you're a fan of DA:O and want more Dragon Age, I definitely think it's worth 10-20 bucks.
"The act of treachery is an art, but the traitor himself is a piece of ****." - Mike Tyson