A general collection on my thoughts on operating system design. Almost definitly horribly organized. I'll probably sort these into a blog post eventually.
http://www.catb.org/esr/writings/taoup/html/ch20s03.html
I'd like to add an addendum. Binary file formats, or at least poorly documented binary file formats. The amount of time I've spent trying to get a lead on sketchups format...
Plan 9 is obviously nice.