Regarding default file manager
The newest edit by James Eder regarding setting the default file manager in System Settings doesn't work. On my box, Dolphin is set as the default File Manager in System Settings and Firefox still opens containing folder with cervisia, at least for me.
Instead of editing the global file, which breaks during an upgrade, you can also edit your defaults.list-- which doesn't break after an upgrade. I've fixed this in my revision.
Had a world of pain trying to get the fonts to look nice in FF after upgrading from Ubuntu to Arch. Noticed that FF wanted to look for the fonts in ~/.fonts.conf, so fixed the interface fonts using $ rm ~/.fonts.conf ; ln -s /etc/fonts/fonts.conf ~/.fonts.conf