It's pretty bad.

Not only it randomly reverts to default sound, it randomly reverts to none (or the volume goes bananas).

I found I was looking at the phone and noticed it was ringing (but no audio). At least twice I was notified of incoming calls via espeakcaller (which, weirdly, works just fine).

At one point I managed to take the phone to may ear while ringing (actually, NOT ringing) and I heard a very faint ring. It's possible the volume goes haywire.

It's also possible someone played with volume while I was showing off the phone. Ringing should not obey the volume level, but adjust it as set in the settings.

One more. Would it be possible to set a boot-time volume? Every time I boot, the logo movie/intro/whatever is very low. Played in the media player (or headphones) it's fine but on actual start-up it's very quiet. Any way to pin the volume to 100% on boot (before the start-up movie plays (Nokia hands, replaced)?