One of the challenges of developing web applications is finding the best way to provide editing capabilities to the end user. Believe it or not the market for web editors is pretty healthy. The question is which one is right for which client?
An excellent comparison (although a couple years old) is available for download
here.
Personally I don't like using WYSIWYG editors, mostly because I can add HTML faster than I can jump to my mouse and back. And even though end users may know HTML – which is an asset – sometimes it can be a bad thing.
I have implemented HTMLArea, TinyMCE and FCKEdtior for clients all with good results. If you're considering implementing a WYSIWYG (What You See Is What You Get) editor, this article does an excellent job of breaking down the strengths and weaknesses of each editor.