Is MediaWiki really "so hard to use"?
My simple answer is: no! :-) ...but I've come to realize that it's not as simple as that for everyone.
Points to consider vis-a-vis my "no" answer:
- MediaWiki gets a new WYSIWYG editor by summer 2012.   - and here it is: VisualEditor (yes, it's here to stay!)
- BBC REPORT: Jimmy Wales says Wikipedia too complicated for many. 
- The panel ‘Wikipedia and the Place of Resistance’ at WikiWars DAY 2 in Bangalore introduced some fascinating arguments about why people either leave Wikipedia (a perspective from US Internet Analyst, William Buetler) or why they’re not interested in Wikipedia (Yi-Ping Tsou about why Taiwan does not like Wikipedia). 
- I've started creating a simplified help page for my students working on Wikipedia. 
- From April 2012: Wikidata to provide structured data for all Wikipedia versions 
- Converting readers into editors: New results from Article Feedback v5 - WM Blog Post by Dario Taraborelli on 25 June 2012
Exploring alternative landing pages
- Wikipedia tests a new signup page - 5 October 2012
Wikipedia's Editor Engagement
- Wikimedia Report for Editor Survey - April 2011
- Best practices in public outreach from Wikimedia Foundation
- Wikidata to provide structured data for all Wikipedia versions - by Daniel Terdiman, CNET, 30 March 2012
- How can we make Wikipedia better? - Flickr album addressing this question at WikiMania2012.