Strictly speaking, the Space Cadet keyboard was JLK's creation (John L Kulp, who ran the MIT Plasma Labs computing facilities, and who went on to help found Symbolics when they split off from the AI Lab).
I had a Space Cadet on my desk in the EECS department along with a Plasma TV system monitor.
Had fun times hacking the PDP-11 software driving the Plasma TV system.
As gumby says, the Space Cadet keyboards, being Microswitch Hall effect-based, were a bit spongy due to the big plastic case, but the switches themselves were dreamy.
By the way, after 40 years of despairing over the loss of Hall effect switches (I nursed a Space Cadet Livermore Labs clone from a group buy for some years into the mid-80's), there are now two keyboards using this technology, and I'm loving the one that's actually available.
The CADR space cadet had a spongy feel, probably because of the large size and plastic case. A sad dependent of the Knight TV keyboards. With the 3600 series Symbolics replaced that with a solid keyboard (fewer keys though) that was more satisfying to type on.
Some of those keys like thumbs up/down etc were never really used anyway.
I had a Space Cadet on my desk in the EECS department along with a Plasma TV system monitor.
Had fun times hacking the PDP-11 software driving the Plasma TV system.