One point: There are two "Themes" options, one which lets me set all the config options regarding themes, and one which lets me choose from the themes. My suggestion is to get rid of the second one from the admin block, and have it as a link from the themes config page. (Failing that, at least rename them so they're not both called "Themes"!
Anyway, nice work. Looking forward to the other SoC projects coming to fruition too.