I have been building a new web server platform and tried to install drush using pear as I have in the past, but it is not NOT the recommended way to install it any longer (who knew?).
Drush has developed a huge cult following for it's ease of use in maintaining multiple drupal based sites very easily from the CLI. I cannot recommend drush highly enough - I can update the code for all of my sites in a few minutes - back in the gory days it would take me ages to do that... These steps worked flawlessly for me on Ubuntu 14.04 today.
The composer references -- the first two bullets -- are from here:
https://getcomposer.org/doc/00-intro.md#system-requirements # See section titled "Globally"
Below that is an excerpt from github (the new home of drush code):