It's one of Jean-Michel Jarre's favorite synths[1].
JM Jarre is one of the godfathers of electronic music. You probably heard Oxygene part IV some time in your life[2].
[1]https://daily.redbullmusicacademy.com/2012/05/jarre-synth
Of course, you can find lots of "boutique" instruments being used by a range of creators. I don't think there are a lot of them only using a OP-1 for full tracks though, although I have seen some live performances made with it together with other instruments at the same time.
Actually this submission seems to be about a few pages, one of them being "made on OP-1" where you can see just that, artists using the OP-1 in different scenarios: https://teenage.engineering/products/op-1/anniversary/made-o...
Edit: one specific example: Diplo claims the OP-1 is one of the ten "essential" items he owns, has to count for something at least :)
> not willing to do any significant part of their job on a device the size of a chocolate bar
Heh, tons of people fiddle with modular synths and I can imagine that being even worse sizes (or "smaller" rather).
Here's a picture he posted of his gear:
https://twitter.com/ebaynetflix/status/442078506655023104/ph...
In his NPR Music Tiny Desk Concert, you can see an OP-1 on the near-right of his table.
https://www.youtube.com/watch?v=heFRwLfjVXI
edit: I found a website which catalogs musicians and the equipment they use. It lists 190 users of the OP-1.
https://equipboard.com/items/teenage-engineering-op-1-portab...
My favorite online presentation of his music is the collaborative video made by Adult Swim for the song "When I was Done Dying".
EDIT: turns out I'm response number 1000 – read someone else's comment.
Who's the thing even for?