If you follow ElephantU's advice and build a super science city (by having all of the city specific wonders (Shakes, Copes, Colossus, Isaacs and sometimes Hanging Gardens) and appropriate infrastructure) the question becomes -- does KRC make sense?
Once the city is full up, KRC will generate an extra 20 shields/turn. Since Engineering could be achieved as early as tech #26, and Industrialization as tech #53, one has 27 turns of use, assuming a tech per turn (of course your mileage may vary.)
I like KRC, and so much so that Ill often delay Industrialization a bit. Even if the trade routes get blocked, the SSC can crank out food camels for the next set of wonders (Mikes. Leos, Isaacs & Magellans) -- and the game seems so much easier & less cash constrained. Also during this era, your government may be Republic (translation: shield poor) for much of this time & Democracy for much of the rest (translation: also shield poor) -- making KRC relatively more attractive.
But keep in mind La Fayettes cautions -- this Wonder (and Copes as well) is much less valuable without Shakes, and less if placed in a city less than full size. -- Also, if by chance youre able to generate a tech per turn from great trades, the six camels for KRC could have been the opportunity cost of two to three techs; and if so the need/value of KRC is less.
