I've been testing out this board for the past couple of days, with a Core i7-4790K and a Xeon E3-1220 v3. All works flawlessly with Linux Mint 16 and 17.
I'm currently benchmarking (using Phoronix Tiobench of course!) a Plextor PX-G256M6e PCIe 2.0 x2 M.2 SSD that arrived today. Too bad I can't use the board's PCIe 3.0 x4 "Ultra M.2" slot, which was a determining factor in getting this board. Aside from the OEM Samsung XP941 there aren't any other such drives, and the XP941 isn't available here.
About the only issue is the lack of lm-sensors support as noted.
This isn't specific to Linux, but I also noticed that you can't boot from an M.2 drive as you normally would a SATA drive. It needs to load the drive's OpROM first, then it will recognize it, and only then can you add it to your boot order. Actually even after it loaded the OpROM it couldn't find the drive to put it in the boot order, I had to disconnect my older SATA SSD before the board would list it as an option in the boot list. If you disable storage OpROM booting in the UEFI the drive can't be seen at all. Unfortunately this leads to the UEFI/BIOS screen loading, then the Plextor OpROM loading, then a pause, then the UEFI/BIOS screen loading again, then the OS loading. With a SATA SSD, it goes from off to desktop in under 3 seconds, but ironically with the faster M.2 SSD, it takes a lot longer due to this. Oh well, I usually keep it running anyway.
This is a good thing though, the Plextor OpROM is what makes it bootable. The Samsung XP941 lacks this which makes booting from it extremely difficult or impossible.