So I've only had a few games with knights: the first few were IRL and Dark Ages only. Many of these games had Rats or Fortress, and both of these are very effective counters to knights. Beggar is also passable in some cases. I played some other games without good engine potential, and once again knights was lackluster, as one might expect.
Then I played a game with no obvious defense, where Throne Room, Laboratory, and knights were all in the kingdom. After buying one province, a few throne roomed knights left him without anything useful in his deck. It seems like a deck that can play multiple knights a turn is really tough to beat. Its like a much better saboteur: it gives other benefit, and there is no "replacement" so 3 piling is harder.
It didn't seem like gaining lots of extra junk in your deck was that effective at stemming the onslaught. Having 2 cost engine pieces does seem to help (squire/native-village/hamlet). Am I right in my assessment though that if an engine is on the board with the knight, and no obvious defense, the game should be defined by the knight battle?
I'm not ready to write an article, but I'm starting to think more about this card.