I have a Reface DX, and it's my most favorite keyboard of all time.

Frist, it is a DX. While the architecture is not identical to the DX7, it is a 4-OP FM synth with feedback on each operator, which gives it a huge tonal range.

Second, the UI is great. And yes, there are 4 realtime controls that make it easy to change the timbre of the sound as you play it.

But the most important part is its compact size and built-in speakers. I've brought the Reface DX to campfires, into the desert, on an airplane, to the top of a mountain, on hikes, to the beach, to the office. I jammed with strangers in the streets of Madrid. With me, I bring cheesy 80s music (FM was all the rage back then), jazz (the e-piano sound on the DX just cuts it), and whatever else I want.