You have to give it to ars technica, they write the best, most in-depth reviews. If you’re interested in buying the new MacBook Air the whole 4-page article is worth reading.
But, to cheat, I skipped to the last page and copied the conclusions below:
The 2012 MacBook Air doesn’t look any different than its last couple of predecessors, but the upgrades on the inside are what make the machine. Although Apple elected not to try and squeeze a “retina” class display into the MacBook Air this year, such a change would have come with great sacrifice to performance and battery life. And let’s be honest—with the MacBook Air, there’s very little wiggle room on either of those metrics. For me at least, I would rather have the performance and battery life.
For someone like me upgrading from a 2010 MacBook Air, or even a MacBook Pro from the last couple years, it would be no question: go ahead and buy one of Apple’s latest MacBook Airs. The performance increase is noticeable even during everyday use (even while using the lowest-end 2012 machine), and Apple finally gives users the option to upgrade from the soldered-on 4GB of RAM to 8GB of RAM in the Air.
Finally, this makes it a more serious machine than it was pre-WWDC, and the battery life of the MacBook Air has reached a respectable level as well. With the addition of Thunderbolt for I/O and USB 3.0 this year, it’s going to be difficult to convince me (or most other existing Air owners) to go back to a MacBook Pro—unless they are hankering for that shiny new retina display or even more significant performance improvements.