How easy is Joomla to use?
A little story here, if you'll indulge me.
I setup a web site for a client a couple years ago. The owner of the site was a complete web-newbie and could only surf the web and answer/write email. He had absolutely no other experience under his belt.
After about an hour of tutoring him in how to use Joomla, he was adding content, items to his shop, along with re-arranging and adding site modules to suit his own needs later on.
Even if I am approached by someone who wants a simple 2-3 page static site, I will still install Joomla (or Mambo) in order to give him/her the power to make changes themselves. No need to call me just to add or edit a simple paragraph.
I believe in giving the power to the client in regard to managing their own website. Joomla allows that. (Not that I don't enjoy the odd call-back

)