Really nice design. This GUI style has a bit of a Smalltalk-80 vibe, with the raster line shadows and old-style fonts.
A tiny observation... The examples box that peeks from the left-hand edge works great, but it's slightly confusing that it's showing the X button initially (when there isn't anything to close yet). How about making this icon initially display as a disclosure triangle (something like a > shape), and then morph into the X when the box is actually open?
I did a lot of setting posters in serif type a year ago or so and came to the conclusion that most tools do a horrible job of kerning.
It did not seem so bad to me at any point in the past (making posters for a college radio station in the early 1990s, making posters for the Green Party in the early 2000s, etc.) I don't know if I got pickier or if a patent war caused regressions in most text rendering systems. I figured out how to manually kern in Powerpoint (awkward but I can get great results) and also a bunch of options in Illustrator that improve things but still require a manual kerning to look right consistently.
I look around and don't see a lot of people setting posters with Serifed fonts and I think it may be that people see they look awful and don't have the knowledge or time to do anything about kerning.
A tiny observation... The examples box that peeks from the left-hand edge works great, but it's slightly confusing that it's showing the X button initially (when there isn't anything to close yet). How about making this icon initially display as a disclosure triangle (something like a > shape), and then morph into the X when the box is actually open?