I had the luck to be able to test a Toshiba Tecra M4 Tablet PC for a few days. You can find summaries of features on the Toshiba and other sites, so I'll just concentrate on the two things I was concentrating on: Screen and mechanical stability of the swivel hinge.
I found the Tecra M4 to be a fast, feature complete machine. However, to use as a tablet, the 14.1-inch screen is just a little bit too big. The screen has a glare problem, especially when used on batteries. I can't imagine the tablet can be used outdoors (in sunlight). Even inside, under a direct light source, the screen mirrors the surrounding in a disturbing way.
The swivel hinge to rotate the screen from notebook to tablet mode made a solid impression to me.
To summarize: I won't buy a Tecra M4 anytime soon due to the screen issue described above.