In article , Alfred
Molon wrote:

I'm wondering how much sense a 4K screen on a 15" notebook would make.

a lot, 5k even more so.

In a shop I opened a 42MP image on a 15" notebook with 4K screen. It
didn't look that breathtakingly sharp.

then something is wrong.

Or to put it differently, is anybody using a 15" notebook with a 4K
screen and is it significantly sharper than a 15" notebook with a 2K
screen?

yes. the difference is significant. there's no going back.