as repetitive as Assassin's Creed is, I definitely kept up with it. Found it more enjoyable--simply jumping from building to building and jumping stabby into guards--than the Witcher.
That was on PS3, though. I couldn't imagine playing it with a keyboard. My issues with the Witcher are the same across similar games, though the Witcher not being nearly as bad (Morrowind, et al being the chief offenders)--encouraged item hoarding and tons of quests that ultimately result in zero story/character enhancement and simply provide tedious distraction.
Having a night/day cycle, that adds to the "wait for the proper hour before x quest activates" factor simply triples the tediousness of these games. I like The Witcher more than Morrowind (too much depth can be crippling, imo), but would rather not endure the tedious and distracting aspects of the game.