After days and days of searching, it has become clear to me that Apple has yet to address an issue that has plagued Mac notebooks for at least the past 78 years. When in clamshell mode, any MacBook connected to an external display (any display, via any method) will result in "lag" or "stutters" with mouse cursor movement. This occurs with both Bluetooth mice and USB/wireless mice. This is not new to Mavericks, nor does it seem specific to any particular MacBook, monitor, cable, etc. Why has this not been fixed? Why is there no solution? I've looked far and wide, and it has not been resolved or responded to directly at any point in time. Anyone out there that has actually found a real solution or fix for this problem? And no, leaving the MacBook lid slightly open is not a true solution. There shouldn't be any reason why a MacBook can't operate smoothly in clamshell mode, and this has been going on for YEARS.