Think I've found my first bug after upgrading to Mountain Lion. I left my Mid-2009 13" Macbook Pro on overnight to download the latest Xcode (using caffeine). I turned off the screen (via the brightness keys) and did the same with the keyboard backlight. Now it wont turn the keyboard backlight back on at all (if you press the F6 key it shows the keyboard brightness popup but it has the little barred symbol under the brightness indicator). Covering the sensor the screen dims ok but the keyboard backlight still stays off. I've tried sleeping, restarting, shutting down, resetting SMC and resetting the PRAM - any other ideas?