In short, most things work fine on Ubuntu 12.10. I first tried using this guide[1] to install Ubuntu 12.04, but had lots of gnarly install issues. I then tried with the regular 'amd64+mac' graphical installer for Ubuntu 12.10 beta, and got it running easily. I was able to ignore most of [1] except for installing and configuring macfanctld, and making the touchpad perform decently using the advice in [2]. (Unlike the author of [2], I hate tap-to-click, so I turned the TapButton[1-3] settings off.)
There are still a few nagging issues I haven't fixed. The Air boots with brightness at the max and won't let me turn it down until logged in, and it loses my touchpad settings on reboot, so I have a little bash script I run to fix them.