Any of the well-known CMS systems should allow for a user-friendly interface. The real difficulty comes in with the setup. I've been building sites on top of Drupal since last December and am still learning the system. It's superbly robust, but also a challenge to fully grasp. Consider it like programming: you can learn enough in a short time to do common tasks, but a full appreciation only comes with time.
More to the point of your post, though, you can drop any of several well-known WYSIWYG editors into Drupal (and probably also in WP and Joomla). That's the way to make content creation/updating user-friendly. I install the over-featured FCKeditor, but have also used tinyMCE, either of which you could also use in your own custom-programmed CMS. My star pupil is a little 70-year-old lady who couldn't be considered web-savvy - she's constantly updating and working on their site's content (
allow me to advertise). My sites have been primarily built for people from rural areas who are less web-centric and far from web-"masters", yet the WYSIWYG editors (coupled with a decent CMS) allow them to take full control of their content. They love it.
FWIW, of the big 3 (Joomla, WP, Drupal), Joomla probably has the most attractive themes/templates available, if that's a factor. Many of the freely available templates are better than some pay themes I've seen for Drupal.
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