To me the big mystery is why anyone still bothers with Liberation, or Deja Vu, or any of the numerous other ugly faces. Libertine is so clearly superior to them all -- even Droid -- there can be no contest where merit is considered.
I jimmied my fontconfig to substitute Libertine for everything except mono (where I use Inconsolata -- thanks Raph). I use Biolinum for window titles, and have altered Libertine so that the traditional looped st and ct ligatures are treated as standard. (One of the disappointments of Google Chrome is that it doesn't substitute standard ligatures. Or didn't, when last I checked. It's been a long time since I looked at Chrome or Google+.)
If anybody can suggest how to persuade (e.g.) Firefox to consider traditional ligatures standard without changing the font file, I would be very grateful.
Likewise, if anybody can suggest how to persuade (e.g.) Firefox to do spacing between bold letters correctly, I would be very grateful.