Hey, sorry I'm late to the party.
Looks very interesting. I'm really excited for all these new experiments in keyboard tech. Here are my thoughts. The Seaboard is pretty different from a keyboard, built from the ground up to put the player in a different mode of playing. The lack of distinct keys is very purposeful, it drags the player (kicking and screaming) out of traditional piano territory, where frankly, most of these products don't excel. The K-board takes a much more conservative approach, and while it might look initially attractive, it might be a somewhat limiting and disheartening. i.e.: the Seaboard is an absolutely terrible piano, but no one cares because it doesn't try to be one.
Now, one of the caveats of a Seaboard is playing vibrato on the B/C and E/F keys. On these particular keys, the distance to a half step is twice as far as it is for all other keys, so vibratos are quite a bit reduced, you have to train yourself to be more aggressive on those keys. Since the K-board's shape doesn't really allow for glissandos between notes, it may approach each note individually, in which all vibrato zones can be tweaked to be identical, even if the key is a "half step key". This is an advantage, but sacrifices one-hand glissandos.
Like any instrument, it takes time to really work with it's idiosyncrasies. Any instrument you learn to work with. And most advantages also come with disadvantages too.
Personally, I'm far more excited about the
Neova ring controller, which is the first and only kickstarter campaign I've actually funded. It handedly reached its first stretch goal, was incredibly well received at NAMM. Totally different concept than the rest, very original. Love the idea of being able to play any controller, but with expression.