Although the wiki page is short and to the point, you might want to add the command for windows users.
When I used
script/plugin install svn://rubyforge.org/var/svn/betternestedset/tags/stable/betternestedset
It obviously didn't work.
And when I tried
ruby script\\plugin install svn://rubyforge.org/var/svn/betternestedset/tags/stable/betternestedset
All it did was a blank line and then nothing.
I believe it's because windows doesn't have its default wrapper for "svn".
So I just ran this command and everything worked out alright:
ruby script\\plugin install http://betternestedset.rubyforge.org/svn/trunk/
(Taken from the SCM in your rubyforge project: http://rubyforge.org/scm/?group_id=2290)
I just think this is a great tool/addon for people to know and use, and just because of this small thing "windows" users wouldn't have a clue on what to do.