more entertainment, from math reviews.

mathematics can be a culture where we use "trivial" to dismiss anything we know how to prove. i never liked that word, to be honest.

some concepts are just hard to understand, at first, and some are just hard.

to quote the review of Gromoν's paper "Fιlling Rιemannian manιfolds" (1983) -

"This paper presents a wide investigation touching various aspects of geometry and contains numerous results.
      ..
The paper contains not only the proof of the inequality (1) itself but also new notions and approaches which allow the author to connect various important concepts and to give them new interpretations."

all well and good.
as for the last line, though,

"The paper is difficult to read."

sometimes you just have to admire honesty. (-: