The Jornada 690 palmtop, with a 133 MHz SuperH-3-DSP and 32 MB of RAM, is my favorite and most used, since it has a good Linux distribution (although fairly aged now). I've used it to help develop code for homebrew 32X and Dreamcast projects (I don't have to upload the code to anything when I want to test it, and GDB is a lot more reliable when you have memory protection).
The Compaq Aero 8000 is a laptop similar to the WorkPad, but it has a 128 MHz SuperH-4. The SH4 gained superscalar execution, 50% more cache, and an FPU over the SH3, so the Aero is actually significantly faster than the Jornada despite the small clock reduction. (IIRC, PDF rendering would take about 50% more time on the Jornada) The display is a 800x600 passive matrix LCD, but it has static image quality on par with an active matrix LCD, with none of the smearing you'd expect... however, the ghosting is still pretty bad.
The Aero 8000 has 16 MB of RAM built-in. It has a SO-DIMM slot for more RAM and can be upgraded to 64 MB, but when I found RAM that worked, I only got half the amount. Apparently, some GPIO lines are multiplexed with the memory data lines, so using the GPIO limits you to a 32-bit data bus instead of the full 64-bits, meaning half the 64-bit PC100 SO-DIMM was unusable. When I got a working 128MB PC100 SO-DIMM, I was able to get it to recognize 64 MB of RAM. (The Dreamcast uses an SH4 variant that multiplexes GPIO with address lines instead.)