It's pretty awful.

I got Dell's "5k" ultrawide before the XDR, and at the time M1 Macbooks couldn't do fractional scaling at that high of a resolution.

The result was essentially a wider 32" 1080p screen. And while the text was crisp, the space efficiency was absolutely awful.

I can't even imagine the 16:9 version of that...

I was originally making a snide joke (sorry) since it’s a popular form factor, and I can’t think of a better common option for 2x scaling than 4k 32”… but on review, I actually take your point on space efficiency, if we’re talking about it as a primary display.

I find 1080p at 27" to be comically big, let alone 32". Maybe my eyes are still young though.