I said "the Show Desktop button and window switcher buttons could be special-cased to have square corners", but I'm not a theme developer, so I don't know whether this is technically possible. If not, the bug needs to be fixed in GTK first.
** Changed in: gnome-themes (Ubuntu) Status: Needs Info => Confirmed -- Show Desktop button (and some others) shouldn't have rounded borders https://launchpad.net/bugs/16045 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs