I have an original MacBook Air, and absolutely love having a full-size notebook in such a lightweight package. I really value the full-sized screen and keyboard, and I bought a very small bag that's easy to carry along with me. Now when I'm out and about, I'm carrying a laptop *and* case that is smaller and lighter than most laptops out there. I even have room for a magazine or a book and a notepad.
That said, I actually don't see anything in these new models that will convince me to ditch my nearly-3-year-old MBA.
"When in doubt, print 'em out." -- Karl's Programming Proverb 0x7