I just implemented my first CMS site using Joomla and had very few problems. The new webmaster has no idea what HTML stands for and she is making updates with only a few problems (she wont read the manual).

I purchased a template and used a lot of the extensions provided from the source libraries at http://extensions.joomla.org/
Installing templates, applications and extensions went well for the most part. Since the vast majority of extensions are coded by others, you never know how good they will install/behave. I was pleased with the majority of exts on Joomla.

It is very helpful to know some HTML and switch to that mode when text just won't behave in the editor. True with any browser editor.

I tried DotNetNuke a while back and gave up after installing so many buggy extensions. I payed money for some of them. Most of the extensions for Joomla are still free and seemed to work better.