@Estel,

I for one would be happy if there was a strict separation between /{bin,sbin,lib} and /usr/{bin,sbin,lib}.

In theory /bin and /sbin and /lib should contain what is required for booting. The rest can and should go to /usr.

Whenever I installed linux in the past I always made a separate partition for /usr and I kept / read-only (also /usr, but that was more flexible).

I just "feels right" to be able to say: this partition is all I need to boot, so I want it separate from the rest.