It's also much cheaper than the Macbook Pro. One of my coworkers that I hadn't seen in years last year came in with an Air and he was making all sorts of comments about how the Air isn't so bad. In reality he felt it was inferior to the Macbook Pros that I and other coworkers had.
I have both an i7 Vaio similar to Dan Fernandez's and a Macbook Pro and the Macbook Pro blows it away.
I now manage code on a .NET app and every time I launch a VirtualBox with Windows Server and run VS2010 all 8 cores of the Vaio face plant when I mount the drive on the host system to edit the IIS website files. This is after I kill every single unnecessary process in taskmanager. That's with all the hypervisor options enabled in the BIOS ect.. and everything optimized, and only a few rows of data in MSSQL just to develop with.
It's depressing to develop for Windows, even with the nicest Windows laptop money can buy.
Sinofsky is just making excuses to charge people more money, because he wants to make investors and Bill Gates happy. That's pretty obvious.