Having the MBA reminds me of the 12" Powerbook that I had before picking up my 13" Macbook. The Powerbook was the perfect size and the right balance of power and portability. The 13" aluminum Macbook is a beautiful machine, but it looks completely huge when compared to the MBA which has similar specs when it comes to processing speed and RAM. So why the change from the Macbook to the Macbook Air?
Well, the Macbook was approaching its second anniversary and even though that's almost an eternity in technology time, it still has a lot of useful life and will sell for almost what the Macbook Air costs brand new. This is a good time to trade the Macbook for the slimmer and longer-lasting battery life of the MBA without spending a lot more money. The eBay fiends will be pleased.
Smaller isn't necessarily better, however. By purchasing the MBA, I lose several ports, take a small hit on speed, get less hard drive memory, and can't load CDs or DVDs. It may seem like a lot, but for me and most people who buy this machine, it becomes a matter of convenience and use as a complimentary device to a primary machine (in my case, a 27" iMac) which does call the other stuff better and faster than a notebook where the MBA becomes the go-to machine for satellite productivity.
So, for now, the MBA and my iPad will become something of a dynamic duo until I determine if one precludes the need for the other. They are very different devices so I don't think I'll get rid of either anytime soon but traveling just became a whole lot easier given the slim profile and full computing power of having a MacBook Air in my mobile portfolio.