I am running Debian unstable with GNOME 3 and MATE 1.8 on a Dell Latitude E6440 laptop. In both, brightness controls (Fn + up/down) systematically put the system to a crawl. This is even more pronounced in MATE 1.8, where the energy saving settings are much more aggressive and keep switching between full and low screen brightness when the laptop is idle.
Anyone suffering from a similar issue ?