I recently installed the 10.8 Golden Master - 12A269 - on an early 2011 quad core MacBook Pro 15" machine. The moment I rebooted from Lion into Mountain Lion, I found a new and most troubling behavior - my command key is "sticky" now. If I press and hold it for 1 second, the system will act like I held it down for 2 seconds. Essentially, any time I press command, it is triggered for twice as long as I had intended. This is incredibly irritating when I am moving fast on the keyboard. For example, I open a new browser window using command-N and then start typing macrumors.com, the M causes a command-M to be triggered and minimize the window. It leaves me wanting to punch the screen. I have reset the SMC. I have reset the PRAM. I have verified the dmg. I have even setup a new partition and done a 100% clean install of mountain lion. The behavior remains the same. Always. I checked accessibility. None of the features like "sticky keys" are on. I even tried turning it on and off. I fiddled with keyboard settings. No other keys are affected, not even the option key. Both command keys (right and left of space bar) behave identically. The 2x interval is exact, so it seems likely software-related. Does anybody have any ideas before I rip my hair out? I am constantly doing unintended things with this behavior.