Apple aren't the first people to do it, but I will never understand this moronic pursuit of thin-ness. Within reason (and I don't consider 1" to be unreasonable) it's not thin-ness that makes a machine portable, it's light weight and width and depth. MBA is all about the looks and showing off the technology. It's not really any more portable than the normal MacBook.
I like the MB Air and I'm seriously considering buying one, as with my wife and three kids we have a direct pass-down path for my work Macs, nothing has to be sold or sit unused. But I can't fault Azurael's comments on design. Ultra-thin is not necessarily the most important or even desirable ergonomic trait in a notebook computer. Less than a third of an inch is *negligible*. As for weight, the difference between 5 pounds and maybe 1.5 pounds is substantial. The difference between 5 pounds and 3 pounds is not in practice particularly that great. For example, on the shelf here in front of me, Johnson's fairly long but good enough recent novel "Tree of Smoke", in hardback, weighs right about two pounds. I throw that in my bag with a 5-pound MacBook or a 3-pound MB Air, I'm really going to notice the difference. I throw in several such books, or a couple of average trade paperbacks with a ten-pound Dell monster, sure, that who package I'll notice.
But when you're talking about carting about in a bag or backpack an iPhone or iPod, a couple file folders, a book, a magazine, maybe a paper notebook, a pen or two, typical mobile kit, whether it's a MacBook or an MB Air, the weight difference is not something that will register. What you will notice, if you're not comfortable with the network optical drive solution or the MB Air will be your only computer, so you'll need that external SuperDrive, is the trouble of packing that in once in a while, and you'll notice with that item on your desk, the MB Air's footprint is actually larger than a MacBook; and if you have an iPhone and don't care to cable switch between the optical drive and the iPhone cable or cradle, add a hub, etc. Quickly, it's not so lean as it appears at first blush.
So at a premium you have less storage, fewer ports of the kind you will actually use, less storage, etc. I've read a lot of MB Air buyers on here stating the $1,000 premium for overall less solid-state storage is just out there, hardly worth it. I think you have to acknowledge it's fair someone will see a $700 premium for twice the RAM but slower speed, no optical drive, no internal optical available period, no analog/optical audio-in line, no included remote, no internal storage upgrade possible, very reasonably priced but time-consuming battery replacement, it's not worth it for a third inch and two pounds.
Again, this from someone who may very well buy one of the $1,800 models, but I do need to have a look at first, hold, use it. If it gives me that feeling of perfect leanness, of ergonomic efficiency and overall simplicity of form, then no matter it's not much leaner, and not smaller really at all, and may ultimately be less simple, with an external or remote optical drive required from time to time, then that premium may be well worth it for me. In my head. Which is really only what counts, if I'm satisfied. But you have to acknowledge it's latitude you're getting on your personal choice of what is, ultimately, almost purely style and afford the same latitude to others' choices of style.
And you do have to admit: You can spend $2,000 on a very top designer's wool suit, or spend $1,000 on a perfectly nice wool suit from a line with less cachet. The MB Air over the MacBook, it's all about that cachet.
