I agree, this piece is neglected despite its being a masterwork. Much of it, I believe, is due to its difficulty. I've had it on my own to-do list, but have too much in queue ahead of it. But someday I'll get into it, and I hope others do too. This is one of the crown jewels of Medtner's oeuvre.
it is difficult, but every time pianists hear it they say they want to learn it... i dont know many personally who played it...
part of it with medtner is that a lot of work you do, is not evident to the audience. this one is pretty obviously impressive, but op,20 no.2 for example takes a lot of work to balance all the vocies, to get the right timing, to get the climax, it is a very, very dense structure and also dense harmonically but still can be delicate, because everything has to be exactly in place.... but that is not really evident to the audinece. so you put a lot of work into it, but don't always get the accolades.
it kind of reminds me of someone who used to complain about chopin etudes, saying that you practice for hours and hours, then on stage its over in 2 minutes. ha!