Very Attractive redesign.
Although, as mclemson noted, the columns are far too narrow. We live in a 1080p world now. No need to cater to 800x600 people.
Also, you might want to address this issue with the forum rendering:
That's been there for me since the last forum version. I'm using IE8, fully up to date.
Lastly, the navigation is a bit... odd. It seems strange to have the "Forums" link buried under the various topic links, although that's not necissarily a bad design. It just makes navigating clumsy. Perhaps including the location in links at the top as the old forum did would be nice.
Also, not having "Post" and "Reply" buttons is poor design, even if the reply box is right at the bottom of the post. Having to go to "Create Content ->Forum Discussion" to create a new post is confusing because it takes you out of the forum you are in and into a separate "posting" section of the site. This is a problem because you can lose track of exactly which area you were in when you were browsing the forums, thus causing one to have to click back and figure out where you were so that you can post to the correct area. This is poor design as it breaks the natural flow of posting by causing the user to have to think about the mechanics of posting rather than on a quality post.The newer navigation style makes it very easy to lose your place as well.
Additionally, the lack of a "preview" button is not good. It is always best to give people the ability to check their post before posting so as to correct ugly formatting and spelling issues before plastering it up on the forum for all the world to see.
I would recommend a return to a more traditional style forum structure with a single front-page forum link, followed by the various sections, and then sub-sections if needed, which all consist of threaded posts ordered by date->mostrecentfirst. Not an exciting or groundbreaking design, but functional and easy to use. And you can still make it shiny if you want.
Other than that, the pie slices thingy doesn't matter to me. I'm completely neutral on that subject.