This is a bit like asking whether a $200 set of headphones are worthwhile over a $50 pair. Or whether native Blu-ray is noticeably better than one that's ripped and compressed. The only real solution is to look for yourself and decide whether it's a problem for *you* specifically, and whether the bigger screen is worth the trade off in pixel density. Different people have very different (and passionately held!) opinions about these things. If you can go into a computer store and look at some side-by-side comparisons that would be worthwhile.
A couple of comments.
- When I used to work in IT support I would often "fix" people's 1280x1024 screens which had been displaying a blurring mess from a 1024x768 input. I was so surprised by the number of people who asked me to put it back because it made everything "too small". They preferred the large blurry mess to the native resolution for the sake of slightly larger text.
- Text is probably the most sensitive to pixel density. Personally I find the pixel density of images and especially videos (including games) to be much less important than with text. I work a lot with large spreadsheets and databases, and with these, higher pixel density makes a really big difference as it allows me to zoom out further and fit more on the screen when the smaller text is rendered more sharply (thus easier to read - my eyesight is pretty good fortunately). While gaming however, I could probably pick and appreciate the higher DPI in a side-by-side comparison, but for me personally, it doesn't offer anywhere near the impact and improvement than it does with my desktop work.
I personally don't have an issue with the 27" 1080P gaming displays... if they're bought by people who will primarily be gaming. The 1440P equivalents tend to be significantly more expensive. I wouldn't touch one myself though, because of the work I do on them.