All possible updates to Mac OS X?
It might be good to not upgrade the system Ruby installed by Apple. Apple installs /usr/lib/podcastproducer, which uses that Ruby, and changing the files could cause it to break if there are version sensitive gems being referenced. In addition, other developers can write code knowing the Ruby is there. 

Use locate *.rb | grep ^/usr | xargs grep require for a file list and the requires.

I prefer to install a new Ruby, either in /usr/local/bin, or by using RVM to install into a sandbox in ~/.rvm and leave my system version alone.

Similarly, Apple's Python and Perl installations are also used by some apps. There's a reason the languages are on there and it's not entirely for our convenience.