Favorite operating systems query

[M.HAAS]

VMS, Multics, MVS, CMS, Kronos, TOPS-10, Ibsys, etc. are all
"just other vendor supported products".  They all have been
or will be "de-supported".  It doesn't matter a bit what
is good or better about any of them (unless, of course, there
is a good idea or two there to incorporate into the portable
operating systems - UNIX and PC-DOS).  To have a favorite
among these is to be stuck with just what the single vendor
sells.  Fine, if that suits your purposes now, but will it
in the future?  Is it worth your professional future to be
expert in one of these albatrosses?

They have a saying in real estate, "Value is measured by three
factors: location, location, and location."  A similar saying
in computing is, "Value is measured by three factors: portability,
portability, and portability."
   Mel Haas  ,  odyssey!mel