It is a cool game. I've finnished it about 2 times, now even with the expantion. But i have to say it is a very buggy game (even more than dd).
Make sure you have the latest patch installed!! It has a very crappy bug: the game simply shuts down without warning or anything. (it seems to be a memory leak.) So good advice: if you buy it and play it: save very very often!!
Its avery big world, can be confusing the fist time you play it. But give it some time till you get the hang of it. After that its fun playing.
I really like the lvl system (is really cool). The story is also very cool. If you've finished the main quest, you can still continue playing and finish every quest you want.
ps: if you get it, buy it with the expantion. Then you'll have a diary system for quest simular to DD. (finished-not finished).
But the choice is yours.
