I never studied communism in any real detail, but what I've so far observed is that: 1) it's one of the closest organisational models to our traditional human state of being, across millions of years (i.e. tribes & clans), 2) outside of Scandinavia (etc), so far it looks like Castro's version came closest to the mark, warts and all?
Also, I find it pretty cool how one can travel around the world and find actual communes in healthy operation, here and there, even in the States!