I have recently become (8 months ago) a MacBook Air convert and I must say, it's an awesome little computer. Not because it's an apple, or has a better operating system, but because it's strong. I have dropped it, the worst being knocked it from a table, both Oz-mark and I missed the catch and it crashed really hard into an open fireplace plinth, right on the stone edge as well.
Any other of my quality laptops I have had over the years would have died, the MBA came out with a few (more) scratches and a couple more dents. Having an aluminium cover rocks.
The operating system leaves a lot to be desired especially if coming from a Windows world, Win7 runs circles around the Mac OS, but the Mac makes some tasks easier for example, I have my MBA with Internet connection sharing, so iPhone defaults to MBA wireless when in range etc.
PITA features.
You need to buy a network cord to make use of hotel wired Internet. Cheap enough on eBay, but yet another cord.
External monitor needs another cord if you are going to use it for work presentations.
No memory card reader. Another cord or stick required.
Good features.
Light
Strong
Awesome clarity on screen in most lighting conditions
Decent battery if you treat it accordingly (I can get near same life on X220)
Rapid cold start up, instant sleep to use it.
Bad features
No user serviceable parts, no user upgrades
Expensive software
OS lacks in many areas compared to WIN
As a playing field leveller, I also have a Lenovo X220 running Win7 enterprise with 6GB ram. Screen size the same approx, weight is a little heavier, startup is only slower as it is full of work security stuff. It has all the bits built in which you need cords for with the MBA, and is an F16 compared to the MBA 737.
Good features
Small
Lightweight
Power Horse running Core i5
PITA Features
All the usual PC issues
My Dream Machine.
MBA body and looks, X220 features and power.
FWIW
Next laptop will be a MBA again, however will upgrade the RAM, something you need a pro to do, and run Windows on it.