Amazed
Since I used this forum to decide on my purchase, I think it's fair to give my test results. I'm a first time Mac user after 20 years of Windows. I wanted portability and a bit of gaming. Quality is not SO important for me since my age is catching up and to be honest, I prefer older games much more then the new releases

All games are tested in MAC ONLY, so no bootcamp and medium settings, when possible shadows off. I wan't able to find the FPS in every game, sry for that.
Doom 3: perfect running
Diablo 3: 50-60 fps in single player, 40 average in party. With ugly combo like CM wiz drops below 20 fps but no impact on gameplay
WOW: same as Diablo, in raids frames can drop below 20 but doesn't affect my playing, since I'm a healer I would notice any delay very fast!
Max Payne 3: No FPS but seems to be fluent, played about 30 minutes.
Total war Rome: No issue at all.
Tycoon rollercoaster: No issue at all.
Splinter cell Conviction: No issue at all
CS GO: No issue at all
TF2: No issue at all
Stronghold 3: No issue at all
L4D2: No issue at all.
The witcher: No issue at all
The witcher 2: Unable to play, even at low settings not doable.
Yes , most games will give a loud spinning fan, and it's get a bit hot in the left corner. Games don't slow down though and the Air doesn't get hotter even after hours of play. The noise doesn't bother me, but is noticed by my fellow players on Skype , even with Headphones on. They don't complain tho, they just hear it.
In short, I didn't buy this Computer for gaming but was hoping on business trips to do SOME relaxing. I was impressed what this machine can handle. Since I don't do HEAVY gaming this AIR was even cheaper then my last 5 gaming laptops with dedicated mid range graphics (last was GT650M) and I don't see any difference.
My spec is I7, 8Gb, 256 SSD, 13,3 inch
I hope this helps the people like the other posters helped me.