I love my Y50. The 4k screen resolution gives me both a chance to see a lot more on a single page and much better and crisper text if I want to see it normal size. The only downside? Software that assumes pixel sizes.
It doesn’t really matter what I am looking at: anything that comes with predefined pixels turns into a microscopic smudge. It’s completely impossible to realize what the buttons do in the Gimp, for instance. Checkboxes are so small, it’s virtually impossible to tell whether they are checked or not.
I can deal with everything else, though. The one thing that is an eternal pain is the web. In particular: sites that define their content in pixels.
User interface design has always been caught between two extremes: on one side, the desire to make everything predictable by forcing it to look exactly as it looks on the designer’s screen; on the other, the desire to make everything work universally on all screens. The former is epitomized by PDF and iOS; the latter by HTML and … the Web.
A PDF document is many things. Most importantly, though, it’s a blob that looks the same no matter where you are and how you look at it. The part where it looks the same everywhere is very useful in certain cases – like if you want to shuttle an official document around, or if you need to ensure that elements don’t get moved out of place.