Just a guess, but you may have in mind certain PS files generated by TeX/LaTeX from the 80s and 90s, back in the day when both PS-based workflows and raster (bitmap) fonts were more common than they are today. So, although it's not really a limitation of PostScript, for purely historical reasons there may be a correlation among academic documents between PS files and raster fonts, which (because of a lack of hinting) look worse on the screen, at resolutions other than the one they were tuned for. For such documents (try this if you have one of them), there is the amazing pkfix tool by Heiko Oberdiek: I had once written a blog post about this (https://shreevatsa.wordpress.com/2011/05/05/converting-old-p...) but you can read the TeX FAQ (http://www.texfaq.org/FAQ-pkfix) or even Wikipedia (https://en.wikipedia.org/w/index.php?title=Pkfix&oldid=71250...) or see it in action in this answer by the author: https://tex.stackexchange.com/questions/120260/making-low-qu...
This highly depends on the software you use and how you generate PostScript files. To program with PostScript, and to display and print PostScript documents, I highly recommend Ghostscript, a PostScript interpreter:
It is available on several platforms and can show the graphical output using windowing systems such as X11. Please see the project's documentation for more information, and consider filing an issue if it behaves in unexpected ways.
The IRC channel #ghostscript on Freenode, and the newsgroup comp.lang.postscript are also good resources to learn more about PostScript and to ask questions.
One interesting fact about PostScript fonts is that fonts are encoded in the same language as entire documents! This shows how versatile and general PostScript is. Here is more information about PostScript fonts:
Really depends on the file, the font format, and viewing program (if you aren't talking about printing). Printed PS can look fine, and is still used in some industries for essential mail. Viewing programs are usually the poorer cousin of PDF viewers, presumably because PDF is much more easily parsed. PDF files tend to use TrueType fonts more, while PS might be using Type1, but that shouldn't matter much.
