I wrote a bit about it here: https://news.ycombinator.com/item?id=19668900
Quoting myself (no real updates since then - too busy with work):
It looks like it has an enormous number of keys, but they are linked together, with each horizontal position being a note, and 3-4 "buttons" on the same physical lever for each note. This makes fingerings very flexible. The closer spacing of the key layout means you can reach bigger chords more easily - I can comfortably play a 10th, for example. The layout is isomorphic, so transposing is as simple as shifting your hands along.
I have played (standard) piano for over 30 years, and this was immediately intuitive for anything melodic. I am far from an expert yet, but the biggest difficulty has been the lack of colours on the keys, which makes it hard to jump big intervals, or play the same note in different octaves in both hands. The lack of colours is because keys don't play a fixed note; the whole keyboard can be transposed by pressing a couple of buttons. Also, because the layout is isomorphic and they were trying to get away from the traditional note system. I am planning to try different colourings with masking tape or post-its, but I wish it had an RGB led for each key (not sure I can justify the effort of rigging that up).
The layout itself is great, and is the reason to buy this. Everything else is less great, and really shows its age (I have the newer model, the CT-312, which dates from something like 2007). The biggest hardware deficiency is the lack of a sustain pedal input, but I expect I can find a way around that with MIDI out or by rigging something up with the (toggle!) sustain button on the control panel. The sound synthesis is also pretty poor, but again, MIDI out.
The best thing about the Chromatone in comparison to all these other alternative keyboards, is that it's (1) Available, and (2) Free! They're clearing out old stock or something, so all I paid was shipping from Japan.