We had about 20 people go through the 40 hour prep course, then eventually take the PMP exam. Only 2-3 passed (not including me). The material is not that complicated, but proving your project time qualification is a pain, and the exam is a absolute mind-****. Even with the PIMBOK exam guide, and a serious effort, I was 3-4 points short (with 20 years of PM experience).
It is of course timed, and in a proctored setting, but in our case, the noise and distractions from other people was horrible even with ear muffs (take your own ear plugs.
Like many certs, it is a exercise in your proficiency of exam taking as much as anything.
I did not elect to pay the $ to take it a second time, as our major gov facility did not do PM in a fashion even close to PMI (which is a bit strange, but OK)
If a company actually uses the method, and pays for it, then go for it.
Bert