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Secondly, I think that certification provides tangible proof to those around me (boss, co-workers, clients) that I strive to improve myself on my own time with my own money. I think they already get that, but it is proof.
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It proves nothing more than the ability to memorize long enough - to regurgitate for an exam. All standardized tests are like this. Whether you have improved yourself or not is better guaged by the quality of your work - not whether you can pass an exam.

For the record, the only exam I ever took as the VFP 3 exam - which most people I knew took. Far fewer took the 6.0 exams. As I have long said, the people that did not take the 6.0 exams is FAR more impressive than those who did.