I have now configured my new 13 inch 2.13Ghz 4GB "Ultimate" MBA so that its programs are nearly identical to those on my old MBP. This includes running Windows 7 in Fusion's Unity mode. Based on a few hours of use today, I am encouraged to believe that my 4GB of RAM is going to be enough. My MBP, which has 6GB of RAM, routinely has no Page Outs. Although I can't claim zero Page Outs for the MBA, it has had less that 5,000 of them, compared with 2.4 million Page Ins. Better yet, the MBA's lightning fast flash storage makes the whole machine seem to run faster. If the kinds of performance I have observed so far holds up over time, I will be a happy, happy camper.