I've encountered the following problems on an IBM Thinkpad i200 running
NetBSD 1.6 with:

auich0 at pci0 dev 0 function 1: i82440MX AC-97 Audio
auich0: interrupting at irq 11
auich0: Crystal CS4299 codec; headphone, 20 bit DAC, 18 bit ADC, Crystal
Semi 3D
audio0 at auich0: full duplex, mmap, independent
  
1. Sometimes (it appears to happen randomly) in the middle of audio
   output the sound will go dead and the only way I've found to regain
   the sound is to reboot. This has happened when using a variety of
   audio applications and the sound is dead on both laptop speakers and
   headphone jack. Could this be a driver or hardware problem? I've
   never had the problem in Windows.

2. There are loud pops and clicks (not good for speakers!) at the open
   and close of audio output (again, doesn't happen under Windows). My
   own workaround to this is to temporarily drop the volume down before
   I hit "play", but this becomes tiring.

3. The default mixer settings have mute enabled on the following, which
   doesn't make much sense:

   outputs.master.mute=on
   outputs.mono.mute=on
   outputs.headphones.mute=on
   inputs.phone.mute=on
   inputs.mic.mute=on
   inputs.line.mute=on
   inputs.cd.mute=on
   inputs.video.mute=on
   inputs.aux.mute=on
   inputs.dac.mute=on
   record.volume.mute=on
   
   The only two not muted are:
   
   inputs.speaker.mute=off
   record.mic.mute=off

   I've also found all the volume levels are initially set to their
   maximum values. It's an easy problem to work around, but I'd be
   interested as to why these are the default values!

Any help would be appreciated.

-- 
Cillian