OK, with 2010Beta2 "as installed", I only had the following channels: Master, PCM and Capture. No other channels, no switches, and nothing for the speaker. However, I had sound working on my previous install of 2009-2 after I built 126.96.36.199 myself. So...
I downloaded 188.8.131.52 from alsa-project.org and built the drivers myself.
I now have the following channels: Master, PCM, Headphone, Speaker, IEC958, IEC958DefaultPCM, Capture, FrontMicBoost, MicBoost and Beep.
And. lo and behold, the internal speakers work!
I believe that's everything working now