I was not really nervous before the exam, but for some reason during the exam the nerves played up anyway. This wasn't really triggered by the questions though, because even though they were sometimes quite tricky and required reading over them two or three times to ensure you've understood things correctly, mostly it was common sense.
The road to certification was a long one. First, I wanted to get it myself. For some reason, that never happened. With my previous employer, after quite some talking, I got it arranged that they would start the process of getting developers certified, but I left before that actually got off the ground.
Ibuildings.nl, however, has the (in my humble opinion) healthy attitude that developers should be certified. So when the opportunity presented itself to get certified, I jumped right on it.
I did some preparation, mainly by reading the Zend Certification Study Guide by Davey Shafik and Ben Ramsey, and testing my knowledge using PHP|Architect's Mock Testing system. And even though most of it was common sense and basic knowledge, I was still happy I prepared. It just helps getting used to the exam structure and content.
Anyway, I passed the exam, so now I am a Zend Certified PHP5 developer. :)