Is there a Wiki with a Web 2.0 UI (like StackOverflow's) ?

Question

I need to use MediaWiki at work. It used to be okay, but with sites s.a. StackOverflow, there's some user interface issues that simply don't do any more.

Most importantly, I'd want to see the live preview when typing. There shouldn't be need for a preview mode.

What Wikis are you using? Which would be the best for a recent (easy) Web experience?

Can MediaWiki be updated to have more recent UI behaviour?

Addendum:

Two products seem to be above others, both "open source commercial" (= you get a skinny version free, standard and enterprise levels with more goodies cost).

• MindTouch DekiWiki
• Confluence

Judge for yourself. I sure found my liking in one of these. :)

Answer 1

Well there is StackExchange (which is the StackOverflow engine), but you have to pay for it.

Answer 2

A discussion on Confluence vs Mediawiki: http://confluence.atlassian.com/display/DISC/Confluence+Vs+Mediawiki

Answer 3

It doesn't have the preview feature you talk about, but you asked for "favorite wikis", so here's mine (at least favorite for ease of use/setup):

http://en.wikipedia.org/wiki/ScrewTurn_Wiki

http://www.screwturn.eu/