A lot of the difference between an IM and GM is a seriousness to the game. The GM is willing to go through all this. He's willing to put up with anything. This shows his dedication. One other thing is the GMs superiority in tactics. For example Christiansen can find tactics in any position. If you're a GM you should be able to overpower the IM tactically. The GM will often blow out the IM in this area.
