I recently took (and passed!) the ZCE 5.3 certification. I've been a Zend Certified Engineer (5.0) for nearly 3 years, and I know a lot more about PHP today than I did then. Today I speak and write various things related to PHP, and also teach all sorts of topics including PHP certification. I thought I'd share my thoughts on the ZCE, and I'll write a follow-up post on how to prepare for it.
The main thing that annoyed me about teaching people for the 5.0 exam in the last couple of years is that it had a topic on the differences between PHP 4 and PHP 5. Personally, I have never worked commercially with PHP 4, and that's true for lots of developers that I meet. So I ended up trying to teach PHP 4 which seemed silly! Happily that is gone now from the 5.3 Syllabus.
There are some new topics and I'm pleased to see the Web Features topic being added. This brings together some HTTP concepts and overall client/server architecture stuff that really helps round out the syllabus. I consider that studying for the exam is in the interests of all PHP developers, these topics are all useful and relevant.