So far so good, although I'm worried this will ruin me for other RPG's.
1. It has choices, the way I loved them in KOTOR, but better. Why? Because the effects of your choices aren't always immediate! As a result, you really ought to think about what you want to do, because the reprecussions might not come around until quite a while later. When something happens as a consequence of something you've done earlier? The game lets you know, too! And those decisions are mutually exclusive - you can't have it both ways...
2. Combat is fun. Your character, Geralt, is quite capable from the get-go.
3. Character development (skills, attributes, etc), is clear, easy to understand, and fairly deep.
4. The characters you interact with are interesting, and you can have conversations with them, make them happy with your or tick them off.
5. The in-game journal is very helpful, especially in that it will tell you when you've hit a dead end and need to do something else first (in regard to the primary quests).
Its a pity this isn't on the 360 or PS3 - I think fans of the RPG genre all around would love this. If your PC can handle it, I can strongly recommend this. Please note that it does earn its "M" rating (check the rating, check the box!), and to th best of my knowledge you can't turn off the swearing and such (does supports Vista's parental controls, though). So, if that's a turn off or you think it might be inappropriate for other players who might use the same computer, consider yourselves warned.