Comment 27 for bug 847001

I'm experiencing this too, using Ubuntu 13.10 on Dell E6530 laptop.

After pressing Fn+up/down, nothing happens for 1-2s, then the brightness is changed, then the OSD for it pops up. I can only change the backlight in steps with this frequency.

During that waiting, the whole system (terminals, mouse, keyboard, ...) becomes sluggish, CPU meter does *not* go up.

I don't remember to change anything related since the install. The backlight stepping works find on the older Dell V13 laptop using Ubuntu 13.04 (though it had its own problems in the past -- one direction keypress behind).