Read all about it!

http://www.dotnetnuke.com/Community/Blogs/tabid/825/EntryID/387/Default.aspx

I'm sure the release will generate lots of questions, please be patient, the Wiki team will try to answer them as quickly as we can!

Looks good, but I have no idea how to use it.  Is there any documentation yet?

Thanks Stupar for the quick quide. Here's an email I used for testing last week. There are features that aren't working, and bugs already entered into Gemini, hope to get cranking on these soon! I'll blog this as well.

Installation:
Install the PA
Add the Wiki Module to a page.
Through the Solpart Menu for the Module Choose Configure Sites
"Add new site" and choose which roles have access to the module. You can choose roles that are authorized to edit, as well as the moderation roles.
Click on the Back Button to return to the front page of the module.

From the menu select "Choose site and door". This allows you to have multiple "wiki sites" that span across a DNN Portal. Defining which site shows up on which pages of the website. Choose the Site you created, and choose the default homepage that is created with each site.
You've now configured the module for use on your page.
You can now use the "plugins" at the bottom of the wiki module.
You'll have a homepage link, that takes you to the front of the wiki.
Edit allows you to edit the current wiki page you're viewing.
Backlinks shows you which other Wiki pages link to the current Wiki page.
History shows you the page history, allowing you to see all of the versions of a page.
MyChanges shows you all of the pages you've edited in the Wiki site.
Pages shows you a listing of all the pages on the wiki site. You can choose from the radio buttons, All Pages, Orphaned pages are pages that don't have any Wiki Pages pointing to them. Strongest pages would be the wiki pages with the most links to them from other Wiki pages.
Search Allows you to search within the Wiki pages, this is not currently tied into the DNN Search Interface, but will be in a future version.
Latest Changes shows you the most recent Wiki pages that have been modified.
Diffs allows you to compare versions of a Wiki page.
Maintenance has some basic maintenance tasks built into the Wiki Module.
Plugins are the same links that are at the bottom of the Wiki pages.
To add a page to the Wiki you need to edit an existing page and put a page name in side of [[]]. So to create a page titled "Wiki Page" you would include the text "This is my new [[wiki page]]". Once you save the current Wiki page you can click on the link that is created to view/edit the new Wiki page. There are further instructions at the bottom of the Wiki Page Editor.