Retina displays. Not sure they were hyped (depends on the definition of hype of course), but I could never set my eyes on regular low DPI displays (e.g. 1080p at 27’’) again, ever, after working with one for a few days.
Have a 24" 1080p second screen which is good for checking content on, and it really just keeps reinforcing how good hdpi is.
I ended up getting Gigabyte Aero 15 with 4K display. It was a great decision.
It's a little like when widescreen monitors came out and people were trying to figure out how to play their 4x3 games.