I’ve been running Suse (12.2 and now 12.3) on a 13" MacBook Air (4,2) as my main notebook and gotten it to the point of working extremely well.
Once you get it all setup, Suse runs beautifully on the MBA. However, as OldCPU pointed out there is other hardware out now that is quite comparable. Dell also has a new ultrabook, and then there is the Chromebook Pixel that looks quite interesting. If you go the MBA route, be prepared to spend some time getting it all to work - hours.
You can pretty much follow the Arch and Ubuntu guides: https://help.ubuntu.com/community/MacBookAir
The main part will be deciding in what partitioning scheme to use and if you want to just boot with UEFI or not.
Some things to consider:
I believe UEFI might have some limitations if you use the Nvidia driver: EFI-Booting Ubuntu on a Mac however, compare this to the information at https://help.ubuntu.com/community/UEFIBooting.
and
Apple uses a hybrid partition table, which you can learn about at Hybrid MBRs
I choose to use the reFit boot manager rEFIt - An EFI Boot Menu and Toolkit
However I then discovered a fork of this called rEFind which I would suggest The rEFInd Boot Manager: Installing rEFInd
(I wonder what Suse 13.1 M4 might install like, especially if using UEFI boot?)
(You can see there is a TON of great information at the rodsboooks site.)
Once you have decided on the boot and partitioning factors, the actual install should be very straight forward.
Wireless, sound, webcam, mic, thunderbolt VGA/Networking, etc. all worked out of the box with a 3.7 or newer kernel.
The Thunderbolt display works, but only really with 3.10 or 3.11 - there is significant input lag with earlier kernels. Hotplug of the display is not supported and likely won’t be.
Installing powertop and laptop-mode-tools can help a lot with battery life (I get ~3 hours).
Lightum provide auto screen and keyboard backlight dimming https://github.com/poliva/lightum
You can get the Apple bluetooth keyboard and mouse to work, but it’s pretty much a huge pain. I can provide the steps I did to get them to work if you like.