I believe the closest to the NEC is the Fujitsu in both performance and form factor. The Fuji has more features, but I like the simplicity of the NEC.
The Compaq has won the innovation design award and seems to be the popular selling tablet, and also has the most pen and performance problems. It's my least favorite device.
The NEC will further define the TPC's use in narrow vertical markets. That's good for the verticals, bad for Mainstream. But then, its not a matter of "if TPC's will take off, it's a simply matter of when".