This week, Sony revealed that it will soon offer its VAIO U ultra-portable PC for sale in the United States. The new VAIO isn't much larger than a typical PDA, but it sports a 5" display, a Pentium M processor, 802.11b/g wireless networking, and runs Windows XP Professional. The unit includes a stylus and virtual keyboard, letting you compose email messages and take notes even while standing up. Although critics worry that the device is too big to be a PDA and too small to be a PC, Sony might very well have discovered a sweet spot with this device. It's an interesting move for a company that abandoned the PDA market in the United States earlier this year