I haven't spent enough time with K to get to that point of naturalness. I do think a k like language that used slightly more natural nemonics could have much broader appeal with minimal impact on code length. IMHO what makes k (and j for that matter) concise is the primitives, how they combine naturally, and how iteration is subsumed to avoid any form "item at a time" code. That last bit is what separates it from the common map/fold idioms in other languages.

Example: http://www.nsl.com/papers/kisntlisp.htm