I am currently pursuing a PhD in theology. It has been a great and difficult journey (commenting on my studies at this point is like a runner trying to describe his joy for the marathon at the 20th mile; more will come on this when I complete).
A decision to do a PhD is a major commitment on a number of levels. For those considering, here are some sources you may find helpful (these sources, save one, are focusing on PhDs in religion/theology fields):
1) There is a glut of PhDs out there. This means that academic jobs are scarce. This NY Times opinion piece delves into this (and other) problem(s). See
here. HT: Taylor Worley
2) Justin Taylor has provided excerpts and a link to Carl Trueman's article in
Themelios. See
here.
3) Ben Blackwell has done a service to all prospective PhDers at his blog,
Dunelm Road. Click
here for a link to some of his PhD pointers.
4) Like Ben, Nijay Gupta has a plethora of helpful posts at his
blog, including this
lengthy essay on the PhD.