BTW, I hope that you upgraded the RAM in the Air to 8GB if you intend to run a VM on it. Trying to work on both Mac OS X and a VM on 4GB is quickly going to get very painful.

TBH, if I was going to buy a new Mac today, I'd go for the new MacBook Pro, purely for being able to have 16GB of RAM. Even with 8GB, my Mac still regularly struggles to keep going when I've got my VM up together with a web browser and XCode (and let's not even talk about Photoshop) on the Mac side.