I understand say OP-1. But how much time on average have you spent on each of those pocket operators? And are you able to use it productively after leaving it alone for some time without checking manual?
The labelling is also pretty good for the first 2 series at least, I haven't tried any of the third. That said, the original official case hid the LEDs which reduces usability substantially - the only useful elements on the screen are the BPM and sync status in the corner.
My issue with them is the lack of a case makes them not very ergonomic and not very portable, for the sake of an aesthetic. All the after market cases have a major downside: doubling the volume (size), hiding elements of the interface, requiring gluing components, price, etc. Also they're pretty expensive for what they are - you really want at least two, by which time you could buy a Volca.
I've thought about desoldering all the buttons and pots to build a more durable unit with bigger mechanical Cherry style switches and bigger LEDs, but I'll never get around to it.
Sure it takes time to reacclimate to the controls but these things are not simple machines like bicycles. The overlays with the OP-Z for example are really handy for quick reference.
As always, its not the instrument - its the musician.
That's going a little far. The thing with music gear is that if you look for people using it, you see it everywhere. But you don't see people not using it. You can't easily google "albums recorded without using an OP-1" and get useful results. So that gives you a very skewed impression about how popular any given tool is.
I'd be surprised if more than 1% of indie releases in the past few years used an OP-1. Heck, it's be surprised if more than 10% used any hardware synth, much less a quirky boutique one like the OP-1.