While LaTeX-based PDFs are generally very good when printed, I find most of them really hard and annoying to read on-screen when viewing the full page. Most line widths are very small, which results in badly rendered screen fonts or e.g. boxes with some non-displayed lines. Documents produced with other software don't suffer so much from this.
try reading this letter on screen in a PDF reader such as Adobe Reader.
or see the box in this document on page 2, at certain zoom levels the left line of the box is not shown)
Besides zooming in in the PDF reader (I don't like that, because I loose overview), or changing the default Latex font, is there an easy way to make LaTeX PDFs more on-screen readable?
For the second example, if you are using Adobe Reader, try going to preferences and turning off "Enhance thin lines" and turning on "Smooth line art" in the "Page Display" category (under the "Rendering" heading).