I would like to start by saying that am only interested in a 37-keyboard midi keyboard with a nice keybed for playing with soft synths (GarageBand, Synth one, King Digital, etc.) on my iPad, connected to my Boss RC-500 looping station. I use a keyboard mainly as an addition to my acoustic and electric guitar(s), also connected to the looping station and amplifier, I do not use the ARP and Chord function. Because of this (playing together with guitar) the Transpose function (transpose whole keyboard up/down semitones) and Hold function (holding a played note) are important to me. And exactly these features, although prominently on the dashboard, are not exactly what you would expect. With the Keystep 37 both these functions work together with the Arp/sequencer and not when playing the keyboard. That is a disappointment, maybe I should have read the 100+ page user manual in advance….
Although the keybed is nice to play I did return the keyboard and, for the time being, keep my Arturia MiniLab III (which has both these features and has a great keybed) as my main midi controller in addition to my Akai Mpk Mini Play (which does not). The Akai I use mainly for the percussion pads, I find the keybed too mini and the keys too stiff.
All the above is a personal opinion and based on the setup in which it is used. The quality of all the mentioned keyboards is very good!