I'm a happy owner of a Dell UP2715K 27" 5k monitor, which is around 220ppi. At 2x scaling, I find it to be a very pleasant pixel density for working with code; text looks gorgeous.
My only complaint is I wish the monitor was a touch larger. I would be very interested in a 32" 8k display when the price drops a little bit; 4k 32" displays just don't have a high enough pixel density for my taste.