Currently our team is using MoinMoin as a wiki for IT and it's so nice.
We want to promote to use wiki for end-users because some of them are interested. On the wiki we'll share and edit requirements of aplications, for instance.
I think MoinMoin is not the more user-friendy (but I love to use it) that's why we are looking for the best user-friendly wiki for end-users/customers
For yourself MoinMoin is obviously user friendly. =) Seriously, consider all users and try to figure what kinds of usage patterns you have. MoinMoin is a reasonable choice since it's such a simple program. You can often help your non-programmer users by adding a feature or two to MoinMoin. Developers are up to speed with it and you have all the content there already.
That said. Mediawiki is used for lots of general wikis out there today. Including Wikipedia. An aspect of user friendliness is recognition. Mediawiki might feel more friendly because users are more familiar with how it works. And Mediawiki is widely adapted. Lots of extra features you might want to add to help your users are already written as extensions. And Mediawiki's extensions API is really good so you can easily automate your own verticals when the need arises. Mediawiki is reasonably feature rich without being totalluy overloaded. It has categories and templates which both come in handy for keeping things DRY and using the wiki in various processes. It shares lots of its syntax with MoinMoin since both have the same ancestor (syntax-wise).
I'd probably go with Mediawiki.
Visit Wikimatrix.org to determine what features you need and what tool is best for you. I often mention Foswiki.org as a very nice and userfriendly tool, but it really depends on the features that you need.