Gabriel: I did check that I wasn't booting into a different kernel. uname -a still reported 2.6.23. I also tried booting 2.6.23 in recover mode, and the bootup messages included something like "hda audio: no codecs loaded". I'll try recompiling again and see what dmesg says on the first boot (when sound is working properly), but it has caused other problems (I can't get Intel 3945 wireless drivers working) so I think the backported alsa is probably a better solution for most people.
Gabriel: I did check that I wasn't booting into a different kernel. uname -a still reported 2.6.23. I also tried booting 2.6.23 in recover mode, and the bootup messages included something like "hda audio: no codecs loaded". I'll try recompiling again and see what dmesg says on the first boot (when sound is working properly), but it has caused other problems (I can't get Intel 3945 wireless drivers working) so I think the backported alsa is probably a better solution for most people.