I went to a presentation at my school a couple days ago about the exam. The presenter made the argument that everyone else in an academic health center needs to be credentialed (dentists, physicians, pharmacists), so we should too. This logic doesn't make sense since they all deal directly with patients, while we deal with populations. He also talked about how this exam might end up being similar to CHES (Certified Health Education Specialist) - which is getting to a point where jobs are now requiring certification. The only problem is that NOBODY has heard about this exam. Very few public health students know about, let alone employers. So, it would take a while to get to a point where this is a valued certificate.
They want you to pay $400 to take this exam. This first time around, they aren't even sure how well the test questions will be written. So, they may give you a "special" certificate - one that's labeled "inaugural" or something similar, so as to differential between the first time takers, and those that took the later, better standardized tests. In addition, your coursework may not have covered everything that's being tested. The curriculum person at my school (an accredited school) said that they haven't decided if they will teach everything on the test, or just tell us which parts of the test haven't been taught to us. You'll have to re-credential at some point - but they haven't decided on when or how.
The overwhelming attitude among students that went to this meeting was that it really isn't worth your time. You're getting a degree from an accredited school, and that alone should be worth something. If anything, maybe this will be a good thing to take once it gets more established in a couple years (or maybe it'll just fade out).