The main thing you gain is crisp and legible small point text for displaying large amounts of code, terminal outputs, etc without taking up large amounts of desk space. I have both standard DPI (~110) and higher dpi (180-220) displays all sitting next to each other at my desk right now. The high res ones look drastically better and are much easier on the eyes. It is quite noticeable.

This resolution is not particularly crazy either, it is the standard DPI of all of Apple's gear for the last 6 years or so and much lower resolution than most tablets & phones. One of the bottlenecks for moving this tech beyond Apple laptops and all-in-ones (of which I am not a huge fan) has been the lack of standard external connections with enough bandwidth for these displays.