The official reviews of the game combined come up with an 81% score (gamerankings.com) with some sites really panning the game. Not so great but the "players' reviews" are much, much better. That situation always interests me. The reviews were like..."pretty good game but with some serious techical issues". Hmmm, I never heard that before about a game.
I tried the demo and thought it was a bit lame. So I took the obvous next step and bought the game. I guess my thought was if players consistenly had good things to say, the game must be better than what the demo showed. Kind of the same feeling I got with SWAT 4. After playing the demo, I thought SWAT 4 was retarded - now it's one of my top 3 or 4 games of all time.
The Witcher definitely gets better and better, the more hours you put into it. I'm playing at 4xAA and 16xAF with everything set to high. I'm very impressed with the graphics. The interior of the castle in the first level is pretty amazing (IMHO). Overall, the Witcher's outdoor landscapes and may not compare with Oblivion's but so far I prefer the building artwork and models of the Witcher by far.
Make sure you patch to 1.2 before playing. And playing the game on Vista is like playing many games on Vista, a crapshoot.