I've been using the FCKeditor with our wikis and it is fine for regular use. So if your users will just be entering text and an occasional table or image it is more than fine. But, if they plan to do things a little more fancy such as adding links or alt-text to images or using templates they could run into some frustration since the FCKeditor doesn't really handle these well and you need to use wikitext. But, the FCKeditor has gotten my users over the wikitext fear and opened up using wikis at my site to general users. Keep in mind the FCKeditor has its bugs but they are few and have not caused any frustration I am aware of for regular users. Plus I let our users know that if they are going to get fancy they should probably be using wikitext anyway.
Has anyone heard where the CKeditor's integration with Mediawiki is going? A few years ago I heard it would happen when they hit version 3.0, which happened more than a while ago. The FCKeditor, while adequate, seems to no longer be in any real development phase. And I was hopeful that Wikia would have some success with their WYSIWYG editor, but evidently not. I understand that the needs of Wikipedia drive the Mediawiki development, but why a WYSIWYG editor for Mediawiki is not obvious I don't understand.