Learning PostScript was a game changer for me. I am so grateful to the Adobe founders for not only the language but the documentation that accompanied it.
This was such an amazing book. I had bought the paper copy and the page where they showed how to put text on a circle was amazing. It is so well written and easy to follow.
I think the performance of Display Postscript in OpenStep / NeXTSTEP was a indicator that NeWS didn't have to be slow. It would be interesting to have a version of it today to test.
I too learned Postscript in 1988 and also figured out how to construct documents in Illustrator's file format (which is a precursor to PDF) so I could export to it. Postscript was a lot of fun to work in (although debugging required some real imagination and lots of paper).