I have done quite a number of sites using Sitefinity.
The RadEditor is actually one of the best of its breed, and I much prefer it to TinyMCE.
However, in my experience, very few CMS admins have the ability to be creating HTML content for pages, and so it's really not the right tool for "users" who can't happily switch to html mode for making minor adjustments.
Personally, I normally implement "widgets" (either Composite or User Controls for the Sitefinity environment) that do all of the "thinking" for the content admins, and manage the html, styling, etc for them. They then just drag the required widgets onto the page, select configuration options, point & click to insert images, links, etc, and enter any minimally formatted text content.
This is how Sitefinity is really designed to be implemented - with the generic-content control (RadEditor) being the fall-back point when something more specialized isn't available or appropriate.