I'm running with the i7 SP3 and on occasion the metro UI will be completely frozen and unresponsive to either my finger and keyboard/touchpad input. I can still move the mouse arrow around on metro but I can't launch any apps or scroll the UI about to other parts of the screen. I don't think it's heat related as has happened inside with cool room temperature. The only option that works is to shutdown --- restart and hope the next boot into metro gives me a workable metro UI. I don't know what causes this as I can't replicate the problem - it seems to happen at random.