Oh, I had the same problem, and the pointer of "Roy Prins" helped me.
You can ignore all previous "guidelines". 12.10 works out of box, without any "post-install things". But the only problem is, with nvidia-driver, you lost the backlight control. (That was the only problem I had, on my 2010 macbook air 11 inch. If I use nuoveau driver, it has the backlight, but some vertical lines comes up. So using NVidia driver is the best bet for Macbook Air 3,1.)
The solution for backlight is simple. As Roy pointed out, add option for "EnableBrightnessControl". For example, my /etc/X11/xorg.conf
tailblues@gilsaire:/etc/X11$ cat xorg.conf
Identifier "Default Device"
Option "NoLogo" "True"
Option "RegistryDwords" "EnableBrightnessControl=1"
And then, it started working for me!