I just recently noticed that my keyboard backlight does not work anymore (when my archlinux installation was fresh, the backlight worked properly with the kernel without any further software).
The f5/f6 keys work properly (the speaker icon appears in gnome-shell when i press the buttons) but the light intensity seems to can not be changed anymore. But i can enable/change the backlight intensity through the terminal typing
$ modprobe applesmc
$ echo 100 | sudo tee /sys/class/leds/smc\:\:kbd_backlight/brightness
Since i didn't change anything on my kernel or modules i find it really strange that it doesn't work anymore.