I absolutely love my macbook air. Had it for about 2 years now. Got the very low end model at the time and use it for software development and photoshop and it runs beautifully. My only regret is not shelling out a few more bucks for a larger ssd (i have the 128gb model). The battery life has been great even after 2 years.

As far as build quality, I'd say its unmatched. I've dropped it numerous times and have never put a case on it. Never even put it in a sleeve. I've left it on top of my car and driven off. It has a few scratches, but thats about it. Maybe I've gotten lucky.