It's a system which isn't impossible to pick up, but is complex-- which works especially when you know where to look for the crit hits (which happen frequently with regular folk and monsters). For real: take a witcher with you, or at least a man-at-arms, or your group is without hope!
I enjoyed the lore about as much as I enjoyed playing, but if there is are a couple of notes it's what seems to be missing. There is almost nothing on the duchy of beauclaire; the monsters manual appears to be VERY lax. I get the distinct impression they are going to release supplements.
It's not perfect, but I have a blast when I play.