Up until this morning, my 15" 2.3GHz rMBP warranted a score of 7.1 for both graphics and gaming graphics in the Windows 8 Experience Index. Logging into bootcamp to play a game, the performance was incredibly choppy, so I re-rated the system. It now scores a 5.5 for graphics and 6.3 for gaming graphics. I re-installed the latest Nvidia driver but it hasn't helped. I know Windows is supposed to default to the dedicated card, but I made sure to lock the 650m in on the OSX side as well, also to no avail. Any ideas?