I can't yet compare to the current gen (my late 2013 is due to arrive any day now), but after 3 years my current iMac screen is holding up pretty well. It's developed a subtle blochy haze in the two upper corners that are very hard to see except on pure white backgrounds. These developed in the last 5-6 months or so. Not sure if it's on the inside of the glass or on the LCD panel itself. It's not (yet) annoying enough to try to fix.