I just bought a MultiMix 16 and set it up with Sonar 4 on an older 1 GHz Compaq Presario. I downloaded the latest drivers (two nights ago), and everything is working pretty well. When I listen to the audio coming back trough the stereo mix via the mixer's headphone output, I hear some occasional pops, but they don't appear to be on the recorded tracks.
I recorded for two hours while we practiced, and at some point (near the end), the driver must have gotten confused, as I stopped getting signals on any of the tracks, even though the mixer appeared to be operating, and I didn't get any driver, system or Sonar error messages.
Overall, I'm very happy with the solution. This is incredible technology for the price, and to be able to record 12 channels (4 vocals, 4 drum mics, 2 direct guitars, direct keys and direct bass) is awesome! I think the sound quality is very good for our purposes (live recordings and demos). If you're interested in hearing the results, here are a few tracks (we're a new rock cover band and haven't been together that long, so please don't judge the performaces!). The only post-production I did was to adjust the levels a little and added some panning. No effects have been added yet.
http://www.pozzy.com/90proof/audio/2006-01-04/Jumpin_Jack_Flash.mp3 http://www.pozzy.com/90proof/audio/2006-01-04/When_I_Come_Around.mp3 http://www.pozzy.com/90proof/audio/2006-01-04/Takin_Care_of_Business.mp3 Theo Pozzy
"90 Proof"