I just got myself a refurbished 15" Series 9 (np900x4b-a02us) (last years model).
After struggling for a while to make the backlight etc work with the UEFI bootloader, I realised my mistake and switched back to using the BIOS. Now I've got the /sys/class/leds/samsung::kbd_backlight/ folder, and when I write '8' to /sys/class/leds/samsung::kbd_backlight/brightness the keyboard backlight is switched on. But it's not very bright. Unless I'm in a completely dark room it doesn't show up at all! Compared with my wife's MacBookAir it's very (very) dull.
Is this a hardware limitation?
(I haven't actually tried under Windows. The first thing I did was to overwrite with Ubuntu 13.04).