I found a reason why anyone would want to use Solaris instead of Linux: Zones. These things are more lightweight than virtual machines or virtualization in the Xen way, but much stronger than chroot. It's especially neat you can make a user root inside a zone, but not on the whole computer.
Pretty cool. Now I want to install Solaris :smt024 . We'll see if I will have time for that sometime. Oh and of course I need to know if Solaris supports cpu frequency scaling, otherwise I won't install it after all (I don't like it when my laptop (centrino = pentium M) gets hot).
I read about zones over here: http://www.softpanorama.org/Solaris/zones.shtml