Running Kernel 3.7.2 on ThinkPad X1 Carbon with Ubuntu 12.10, can confirm this exact bug.
xev shows this when hitting Fn+Brightness Key:
RRNotify event, serial 71, synthetic NO, window 0x4a00001, subtype XRROutputPropertyChangeNotifyEvent output LVDS1, property BACKLIGHT, timestamp 1441820, state NewValue
Running Kernel 3.7.2 on ThinkPad X1 Carbon with Ubuntu 12.10, can confirm this exact bug.
xev shows this when hitting Fn+Brightness Key:
RRNotify event, serial 71, synthetic NO, window 0x4a00001, tyChangeNotifyE vent
subtype XRROutputProper
output LVDS1, property BACKLIGHT, timestamp 1441820, state NewValue