I've just discovered the prototype, and I want to write down my first impressions before any other rational analysis:
- I miss Wikipedia puzzle-ball logo. I've later discovered that it can be seen by zooming out to 90%, but the first gut feeling was one of a void, bare, unadorned page, not aesthetically pleasing. Recovering the left column with the logo made that impression go away.
- I love the clean, modern design, new layout for tools and navigation, and the right sidebar with useful, contextual tools! Good work.
Accessed on chrome browser on Windows 7.