Hypersphere rings are awful (sorry mr. hypersphere, just think the Topre OEM variant is 1000x better)
75% layout is overrated
thin keycaps are really nice on clicky switches
I really don't like aluminum keyboards anymore.
I prefer plastic cases. To me they feel more durable (if dropped) and I like the extra flex.
I've never heard of anyone actually liking flex in a keyboard.
This would depend on the type of key switch being used. I would not want flex in a linear switch keyboard, or a plate mount clicky switch keyboard. I would want
some in a PCB mount (or half-plate) keyboard with tactile switches, to increase tactility. My Filco Majestouch with browns has a bit of flex and feels great to type on (even though it has full plate).