I recently installed chrubuntu on my acer c720. The is one Problem thou it won't let me boot back into chrome in less I reset and delete ubuntu. It also works the other way round so that when in chrome OS can't access chrubuntu.
Some Extra Details. I am running on 13.04 because 13.10 is really laggy on my chromebook. I only accessed chrome os because I run the command that set defaults at the 5 second at the end of ubuntu installation