I'll actually post for once, why not?
Being new to Dark Ages, the Knights were certainly the hardest aspect for me to deal with so far. I don't think my early brainstorming on the set was horrible, but I definitely did a poor job of accounting for Knights specifically. Werothegreat's constant assault exposed my capable, but very narrow engine in a few games. I did much better in the games without the knights; I believe the one I won did not have them, though I don't remember.
They have some qualities similar to Saboteur in that their value increases with better drawing and the opportunity to play them more often, especially since it doesn't wander through your deck until it finds something worth it. However, unlike Saboteur, the cards do something for you, and there's the burning question of...should I take the knight that's less useful for me, if it will still may help me gain an advantage over my opponent? I guess it depends on the game. Knights' value may change based on the kingdom setup more than most cards.