Think you will find machines based on cortex (unless software/drivers are badly implemented) will be considerablly faster than any xscale devices.
I have used so many xscale based devices (including some with poropper GPU's) and have never been overwhelmed by their speed. In fact In the Win CE world I have a 206Mhz strongarm CE device that will browse the web considerablly faster than a number of devices with 400-533Mhz xscale and one with Ati Imageon when browsing and doing in normal tasks, using GUI (in fact even outpaces the xscale in PIcalc up to 200,000 decimal places where after they seem to offer almost the same results.)
IMHO with all the places we will see cortex cpu's can't see it is worth persuing any devices with xscales in them
Still who cares. Beagle board project is great and there is going to be a netbook with a beagle board inside it...