As of this time, I consider the main problem with different OS's and
desktops built on OS's etc. to be this:
For one reason or another, fairly large numbers of applications have been
built for or ported to, one OS (or 2 OS's) but not others. Whatever
your preferences, if you need certain applications bad enough you
need to get and put up with the OS's they run on.
Yes there is (in principle) ``Java'', compilers and ports, developers
who can be convinced to -- etc. But these things are often more difficult
than just putting that CD in the drive and installing the whatever OS.
Right now there are probably about 5 major OS's that might have something
you need written for one or more of them. For instance, there is a lot of
useful freeware written, alas, for win 9x that is simply never going to
see the light of another OS, probably not even future winblows as it
inevitably moves towards non-backward compatibility.
Freeware is especially annoying since, it is often hard to even
find the original author, much less the source code.
