I don't even use HDR, the density is just that good for looking at text all day. It takes on this milky quality that I haven't seen on any other monitor before this.
The complete lack of appreciable IPS glow or uniformity issues is also better than you might expect for text. Especially with dark backgrounds which will now present one impressively uniform block of color, improving contrast.
Obviously there are people who need the higher PPI, but if you look at text all day I'd recommend giving 4k a try before spending 3-4x as much on a 5k. You can run the 4k display at 5k, the same way that you can run a MacBook Air at 2880x1800 even though it's really 2560x1600. Modern scaling algorithms are very good.
Personally I would much rather that they made the display 4K and 120hz instead of 5k and 60hz. At that size, I don't see a big difference between 4K and 5k, but the 60hz vs. 120hz jump is very noticeable.
> most 4k displays were 27".
This is in the direction of lower PPI/DPI, which is worse. That is:
4K @ 24" > 4K @ 27"
Also, as others have noted, the Apple Studio Display is 5K, so more UI is visible than on a 4K monitor.
I'm sitting in front of a 4k 27" and the 160ppi is almost indistinguishable to my macbook at 227 due to the different viewing distance.
And I always had the impression most 4k displays were 27".