I like many things about my MacBook Air. It's a gorgeous piece of hardware loaded with flawlessly (mostly) working software.
But the thing I really like the most is it's near-instant-on ability. It's only comparable to an iOS (or Android) device. I can pull it off my backpack, have it on and running in my lap in ten seconds and I'm ready to rock. I cannot compare this to any Windows PC or laptop I have ever had.
And I had quite a few.
Why is this important?
First and foremost, the psychological barrier for starting doing something is much lower. I might be lying on the sofa, watching a TV show, and then I can take the Air and check that PHP script I wrote earlier today. And I can do this in the ad break. When the show is back, I would simply turn the computer off (for like 5 seconds) and continue watching. Good luck doing that on a Windows based laptop.
It's just so much less distraction.