We like Cities & Knights the most of the expansion packs, but we prefer the regular version.
The rules for the 5-6 player expansion state that every player is allowed to the opportunity to build at the end of EVERY player’s turn (rather than only being allowed to build during your own turn, as in the regular rules). You’re technically supposed to go around the table and ask everyone if they want to build. I just find that it adds a LOT of time, and people normally forget and it causes fights, etc.
If I do play the 5-6 player expansion, I normally try to get people to play that 1) we forego the building phase or 2) if you want to utilize the building phase, then it’s your responsibility to vocalize it before the dice are passed. We are not going to ask every player every time.
Maybe I’m just impatient and crabby?