This is important and it's a bit of a disgrace that so few reviews have benchmarked this. One of the biggest changes between this Macbook air and the 2010 Macbook Air was the removal of the NVIDIA GPU. Why wouldn't people want to test the impact of this?
Plus, with Valve's "Steam Cloud" initiative, the idea is that you can pick up any one of their games and continue on from where you left off on a different device, no matter where you are. This is especially true for TF2 which has just gone free to play.
Gamers want to leave their gaming machine and be able to play TF2 on their low-powered portables.
I saw some benchmarks for Portal 2 which uses the same engine as TF2 on OSX Daily if that helps:
http://www.steamgames.com/steamworks/ov_cloud.php
P.S. @nonameowns Idiots like you hold the internet back from being great.