I did own a couple of 4000s because I was intrigued by its good reputation as well as its design.

While the general ergonomics is much better than it is in standard keyboards, I've never liked how much force is needed to push a single key. And I don't mean just compared to mechanical keyboards or scissor switches -- the keys needed more force to press even compared to other rubber dome keyboards that I own.

While the palm rest is great as is the curvature, when it came to daily use and pushing the resisting keys, it simply wasn't as much a joy for me as for stickydink.