I discovered Wikipedia in February 2004, and was delighted with what I found.
My reaction to what I found available in the mediawiki software was that "microsoft word is a zombie".
Seriously, why should most of us want to use software whose primary purpose is putting words on paper? Creating printed paper is mostly not what we do anymore!
I have been using computers for so long that using wiki markup is actually easier and more natural for me that wysiwyg, but I do believe that is not the case for most potential users. In my experience, the lack of wysiwyg editing is the most serious barrier to adoption of mediawiki by newbies.