since chrome os is a slimmed version of linux, i dont see why you shudn't. a linux distro like ubuntu or fedora is definetely an upgrade.

I'd recommend Ubuntu 14.04 (linux) as it's stable and it has long term support. If you don't like the Unity DE, you could always install KDE or Gnome shell over it

Just go with debian distros ^ as it tends to have fewer issues (from what I have seen). And give < elementary OS a go (It is not a rip of Mac OSX, it's so much better).