The site: http://naatan.com/support/
It's basically made to fit the style of http://naatan.com/.
Surprisingly most work went into getting all the colors right. The default XenForo theme is really made for light themes and if you want to categorize your colors differently from the way XenForo does it you are in for quite a job. I found myself often switching between messing in style properties to editing the css templates manually because certain values weren't covered by the style properties. If there's one thing I'd like to improve on XenForo it would be to have a better default theme that makes full use of the style properties, but that would likely be a humongous job.
Aside from that I also spend quite a bit of time getting the sidebar working properly, sacrificing popins in the process, but I'm ok with that given the simplistic style of the site. The page switch animations were already custom made for my main site so that wasn't a lot of work to port over.
All in all, what I've learned from making my first XF site is that you can throw a theme together extremely fast as long as you're ok with just switching colors or images, but if you really want to visualize an idea that you have in your head you're in for quite a job. Of course that's the same case for any other bulletin board, and XenForo gives you an awesome set of tools to get the job done right, which is more than can be said for most of the competition out there.
Note that I haven't had a chance to test it on all browsers yet, so if you see any obvious problems please let me know.