Been playing with Plan 9 From Bell Labs.
Man is that counter-intuitive. Unix was all about minimalism. BSD and Linux still are, at the kernel level anyway (let's not talk about GUI wars for a moment.)
Plan 9 is even more extreme. Think of a bare X server (no window manager, etc.) and you're close.
No title bars, nothing even vaguely like 'help' or even 'intuitive icons' (or icons of any kind.)
Getting kind of used to it, but I'll never do anything serious, I think. More's the pity.
Take a look for yourself.