Also, svn has one huge advantage: it reignited popular work on VCSes.
Remember what things were like before Subversion? You could use CVS, or if
you really wanted to drive your developers insane you could use arch.
Now? *How* many possibilities have we got, again? Yes, most of these
ultimately derived from arch or bitkeeper or something else distributed,
but I'll bet that the impetus to work on version control at all ultimately
came from the fact that, well, people *worked* on subversion, it's *not*
as hard as everyone has made out, and it doesn't need to be terribly
boring after all, and CVS et al has all these annoying wrinkles which SVN
hasn't quite squashed...