Normally the top left hand side seems to get warmer then the top right hand side even though the fans are in both locations. I noticed that just above my Function keys F1-F5 is a little warmer then the right side, however if you really start to tax the 9600 GT after playing something lide COD4 for an hour you can possibly cook an egg on the upper left hand side, but it cools down really quick. When just operating with the 9400M it is not so bad, but once the fans kick in for the 9600 GT it gets warmer which is normal unless your MBP starts to shutdown because if it, this is not normal and has happened to someone I know, turns out they had a bad fan.