My three categories would be:

1) Phone/PDA - three to four inch touch screen, light weight, long battery life. This is the device that is always with me. I want to get and make calls; keep a schedule and have it beep at me to get me to meetings; let me jot handwritten notes (recognition is a bonus); let me do light browsing; and have enough simple games to keep me entertained for minutes at a time. This is the device I keep with me when I go to the bathroom. This is where the N900 or Droid would fit.

2) Portable Computer - about a 5 inch touch screen (ideally capacitive plus an active digitizer); under 1 pound; physical keyboard and mouse (the latter ideally via trackstick or trackball); 1.5-2.0 GHz CPU, 1-2 GB RAM, 16-64 GB SSD; support for standard USB peripherals (keyboards, flash drives, etc.). This is a device that I might not have in the bathroom but I would take to lunch and to meetings. This is my OQO and might be the UMID M2.

3) Desktop Computer - whatever $2k buys when I buy it. Currently I have an Dell Studio XPS built around Intel's i7 Bloomfield and geared towards general processing (versus graphics processing).

The UMID doesn't compete with the N900, it competes with the netbook and laptop market.