Blizzard did another round of beta invites a few days ago I received an invite. Though I liked playing the beta on my HP better... my MacBook Air played it just fine. I had everything turned on low with the resolution set on whatever the lowest that was still 16x10. I also set the effects off. My fans were going full blast during the game but I normally use my iPhone headphones with my air anyways so I did not hear it.
Come on, seriously. That is nowhere near "just fine". And you are not gonna convince us that the stock iPhone ear buds help in any way toward noise cancellation.
I have been playing the beta on a '11 13" MBA and it is not really what I would call an enjoyable experience. Playing it on a friends desktop at high settings and antialiasing with a perfectly smooth frame rate, was an entirely more enjoyable experience.
I realize that is the way I will have to go unless either, MSI release a fantastic external GPU at a fair price, or Apple release a fantastic 13" MBP with a discrete GPU that somehow stays quiet and cool at the same time.