Also keep in mind that PostgreSQL provides unparalleled programming possibilities. I don't think it is humanly possible to fully master every possible aspect of PostgreSQL. Consider what this means:

1. Mastering standard data modelling techniques

2. Mastering advanced, PostgreSQL-specific data modelling techniques

3. Mastering server-side procedure programming in a large number of languages (C, Perl, Lisp, TCL, PHP, Python, Java, ...)

4. Mastering server-side type/language handler programming

5. Mastering tuning PostgreSQL to the OS, and tuning the OS to PostgreSQL

6. etc. This list can probably go on forever.

The best you can do is master a significant part of things and use that to carve out a niche.