Perhaps just to stir up the hier controversy, spiced with PATH 
opinions, would it not be possible to create dynamically linked 
versions of the /bin/ and /sbin/ commands to be included in /usr/bin/ 
and /usr/sbin/, respectively, so that /bin and /sbin can be completely 
dropped from anyone's $PATH?

I've always been wary of the fact that there seems to be no real 
convention as to which of /bin and /usr/bin should occur first in the 
path, this at least eliminates one such indecision :-)

One small gain (at the expense of a small disk capacity loss) is the 
saving in memory and loading time this would provide.  But having a 
simpler $PATH does appeal to me.

I do have far more radical ideas about the arrangement of hier 
directories, but the time is not yet ripe (nor my opinions) to voice 
them here.

Regards, all.  Lucio