Yes, it does. The particular thing I had in mind was a web app that currently supplies on-the-fly generated PDF files to its users. I have had a number of requests to give users the option of PS format (for various reasons which don't matter here).

pdf2ps doesn't, AFAIK, exist... and even if it did, I'm not sure I want to deal with the disk caching such a thing would require (I hate temporary files, and I don't use them unless I must).

So, despite the value of your comment, I'd still like a similar interface for creating PS or PDF files.

I have pdf2ps on my machine. According to its documentation, it is a wrapper around gs (aka ghostscript). Taking a look at the documentation for gs, it looks like it will happily take input on STDIN and send output to STDOUT. (It says that it wants a switch to tell it that STDIN is coming on a pipe so it changes its default behaviour about when it has received all of its input.)

I haven't played with it, but this makes it look like you can develop versions of both utilities that operate without any temporary files at all.