@ ransom - I hope you’re right… I managed a WPF project last year and the consultant used MEF in that project. I took a brief look at it at the time in reviewing his code. It wasn’t at all easy to follow. But, he had several frameworks in use and I wasn’t entirely certain which part was MEF and which parts were something else.
@ eric - It does get harder every year to understand a lot of these new frameworks 
@ architect - Does Prism compliment MEF or is it an alternative? I believe MEF has already been selected at this point. I’ll know more in a couple weeks.