[GeoffR]

I am a human and I can easily see the quality difference between 600dpi and 1200dpi with laser printed text, so the idea that the human eye cannot tell the difference is simply nonsense.

(Edit: That's not to say it is a particularly important difference, there are other things that are much more important for reading than high dpi, such as using a well-designed font, good typesetting, fine-tuning layout to suit personal preferences, etc. )