Ian Murdock on Solaris...

If you want another example, one from a company who any developer would agree is an outstanding engineering organization, here's one: "Sun has maintained binary compatibility between operating system releases for nearly a decade, enabling existing Solaris applications to run unmodified on Solaris 10. This means that Solaris applications developed 10 years ago will run on Solaris 10 unchanged, taking full advantage of new and advanced Solaris features."

Yes, it's true that there is outstanding backward binary compatibility in Solaris. However, if you're going to try use that as an argument in favour of Solaris, try again.

Have you ever actually used a Solaris system?

• The ugliness on a Solaris system starts with $PATH, which is all over the place: /usr/ucb/bin for the compiler, /usr/gnu/bin (IIRC) for bash, /usr/bin for sed. The FHS is nonexistent.
• Everyone who writes code for the Berkeley socket API knows that Solaris has to be different:
  

  #ifndef sun
  int yes=1;
  #else
  char yes='1';
  #endif
  

• Even if you do it that way, on Solaris you have to say -lsocket.
• I've heard claims that Solaris, partially because of the backward compatibility, is rather slow; that Linux beats the shit out of Solaris on the hardware (SPARC) that was more or less specifically designed for Solaris (and vice versa). Having used it for a short while once, I cannot think of a counterargument for that one.

If you're going to say that backwards compatibility is good and that we should incorporate backwards compatibility into Linux somehow, then please do not point people towards the two ugliest operating systems on the earth with a lot of garbage baggage for the sake of backwards compatibility...