FreeBSD, Bitching about GNU
I think part of it is the fact that it doesn't bother with GNU software, which, given my sudden shift towards hating the GNU Project, probably explains a lot of it.
Of course, half my bitching about software not working on FreeBSD is that the GNU Project has its tentacles SO ENTRENCHED into UNIX{,-like} software that everything expects their stuff to be there. Thanks, GNU Project. I hate it.