Dear Brandon,
thanks for your marvellous essay on Wikipedia:Wikipedia Signpost/2012-08-06/Op-ed.
Feedback: The current approach is great for all the reasons you've heard a million times already. I associate myself with those criticising the prevailing black colour and prefer a dark gray (see below). While the implementation of a variety of features is already visible in your mockups, some are not - that's great and part of the process. Noticing the inability of an average user - independent of age, gender, educational achievement or profession - to find the sister projects in a Wikipedia article is a pain in the arse. The Beatles mockup involves a gallery at the top of the article, which is a step in the right direction. I'm clueless on a proper way to indicate sister projects where appropriate: when looking on the article about en:Germany I might actually want to see more images about it in a convenient way.
Landing pages: Several domains such as www.wikipedia.de www.wikipedia.com and the like are currently controlled by a variety of people and institutions. Those with affiliation to the WMF could rethink the design of these pages as well. Crawlin the web some time after your presentation at Wikimania I noticed this redesign approach: http://www.chipotoole.com/wikipedia.html - the simplicity of a Google-ish interface speaks for itself. The homepage design approach features a dropdown solution to search for images and other stuff. Searching for images could be a great feature - it'll automatically forward people to the Commons. However, redesigning that platform is a utterly different project ;)
Footer: The footer of http://reportcard.wmflabs.org/ makes use of a dark grey as well. The three column layout and WMF's slightly darker logo result in a rather subtle, inconspicuous impression. Looks good to me. An embossed WMF logo could be appealing as well.
In a nutshell: I don't intend to say that these suggestions are the best solution - in the end any design approach remains a question of personal taste. A combined colour swatch of white, blue (see header section of the reportcard - similar to your edit button) light and dark gray features both: a reminiscence to the current design and a fresh, new interface experience. Your feedback on my suggestions above would be appreciated.
Regards,