am just using out-of-the-box kubuntu 12.10 64bit on an UX31A, BIOS 218, and about everything is working properly, even now the fn-f5+f6 for screen brighness control, found a simple fix for it on another thread here, http://ubuntuforums.org/showthread.php?t=2006790&page=5 post #47:
UX31A -- A simple way to fix the brightness Fn keys
This does not involve changing the kernel.
I tested it with precise, using both the standard 3.2 kernel, or the upgraded 3.5 kernel.
Change kernel command lines in /etc/default/grub as follows
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash rootfstype=ext4 pcie_aspm=force nmi_watchdog=0"
GRUB_CMDLINE_LINUX='acpi_osi="!Windows 2006" acpi_osi="!Windows 2009" acpi_osi="!Windows 2012"'
Then run update-grub.
After rebooting, the screen brightness function keys work.