Sony will be announcing a Flash version of the UX50 UMPC which will come with 16GB of NAND Flash instead of the 30GB hard drive. Sony will be announcing more details on the Flash version later in June. Despite the cut in storage space Flash memory offers a lot of advantages. It uses instantly-accessible, non-moving NAND flash memory instead of the rotating discs found in hard drives; therefore it can upload and download data quickly and quietly with minimal power consumption. Though it weighs only half of a comparable hard drive it accesses data three times faster and writes 1.5 times faster.

As it does not have any moving parts it uses just 5% of the electricity needed to power a hard drive.
Related – Sony VGN-UX50 is official