Quick note: when I started using Phonon everything Just Worked(tm), including Skype and Firefox and mplayer and DragonPlayer and Amarok and ... everything cohabited and was beautiful.
I upgraded my operating system and was "blessed" with PulseAudio. Now nothing Just Works(tm).
This is the difference between a system well thought out (Phonon) and a system so convoluted and in search of a problem to solve that it simply messes it all up in the process.
I had no need for PulseAudio. I had Phonon + Xine and Phonon + GStreamer and life was wonderful. I hope, based on my personal experience with PulseAudio, that others wake up and realize that, no, it's not necessary and that yet, it does complicate things and that, why, we'd prefer things to Just Work(tm) versus become a mess.
I've seen the block diagrams, I've been to conference presentations explaining how it works. The insane complexity of it all horrifies me.
Regardless of what others say about PulseAudio, I will not drink that kool-aide.