I can attest to this too. The Planet T is the only keyboard I ever sold and not at some time after regretted it. The action was horrible. It was barely touch sensitive, the energy in the tine came from lifting a 'sticky' rubber pad, and when it couldn't stick any longer it release the tine, the difference between softly playing and hammering was not very great at all.
Particularly hated the fact that there was no sustain pedal, you could just about get away with a reverb pedal to 'fudge' that
Also as the key release was basically the rubber pad dropping back onto the tine, in the lower register you could get a lovely farty noise as the tine vibrated against the pad.
But as a teenager, in the 70s it was a way for me to have an electric piano because a Rhodes or Whurly were well out of my reach. Also it was basically its own flight case.
I really can't believe the prices they're fetching now.