I have been reading news lately about two devices coming soon: the HTC Athena and Tatung.
These devices have been called by the OEM or by the press UMPC, and I think that the reason why is because of their size. In my opinion they should have been called PPCS which means Pocket PC on Steroids. Yes, these two devices use Windows Mobile 5, based on Windows CE. This Operating System has a lot of advantages like Instant On, a very easy to use Calendar and an Easy to Use Contacts. But it has a huge to me disadvantage, it can't run the millions of programs available for Windows OS for PC. This disadvantage is what has pushed me and many others Pocket PC owners to buy a UMPC.
Of course, this is another valid option for some. But... Don't let them lie to you. You are buying a PPCS not a UMPC. Be sure that you are buying what you really need.