Avoid users as long as possible

Paul Graham has a great article, on what makes a language popular, and why Lisp never achieved critical mass. One comment I found particularly funny:

choose your users carefully, and be slow to grow their number. Having users is like optimization: the wise course is to put it off as long as possible.

As a writer of routines, libraries, and even programs that others have had to use, I can completely empathize with him. But as a user of other's routines, libraries and programs; I would borrow from Einstein and say: put it off as long as possible, but no longer.