I posted this in another thread, so I'll just copy & paste. In short, FM + MBA is a match made in heaven. Even on the 11". As FM is extremely CPU intensive - get the i7 if you can afford it as the poster above said. Even though I haven't tested performance on i5 vs i7 it's all reason points to that. FM is all about processing.
Edit: Also get 8 GB of memory...
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Just wanted to add my thoughts on how Football Manager 2013 is running on my MBA 11" i7/8GB as I myself tried googling how playable it was on the MBA 11".
Football Manager 2013 is a massively CPU intensive game, and on the MBA 2013 it's quite fast. You obviously won't get the full 9 hours, but it'll give you around 3-4 hours if you play it non stop. The machine also gets hot at times - not unplayable hot, but the fans speed up. Heat is a problem on any laptop running this game as far as I know. When it comes to watching the matches the animations are usually smooth, although when you're running low on battery the game gets slower - my guess is that some power saving mechanism is disabling the turbo boost of the CPU.
The biggest issue with gaming on the MBA 11" though is the screen resolution as the window gets pretty cramped. It's fully playable, although the 13" might be the better option both due to the significantly larger screen and the better battery capacity. For me the MBA 11" is perfect even though the screen is a tad cramped and the battery only gets you as far as it does.
One thing that might bother you (it did surely bother me) is that Football Manager 2013 in full screen mode doesn't support the native OS X full screen mode. This means that in order to do other stuff (e.g. swapping spaces) whilst the game is running the game is forced into windowed mode. The problem with the original windowed mode is that the minimum height of the window is 800 px, whilst the MBA has a height of 768 px.
To fix this you'll have to force a "--small_window option" when launching the game (Set launch option, add --small_window). You'll also have to press "maximize" window (green button) in order to resize the window to fit the screen so the bottom of the windows isn't off screen. You can also change some OS X settings in order to hide the top bar whilst playing (instructions on how to run it smooth here:
http://community.sigames.com/showthr...=1#post8880711).
Summarized - the MBA plays almost perfect with the 11" and 100 % perfect on the 13". Game on!