There has been an interesting discussion on an internal Microsoft mailing list regarding the certification process and exams. I've seen posts from many people that are very experienced with products saying they can't see any point in the certification exams and that competencies in the Microsoft Partner program shouldn't be based on exams. They feel these people should somehow just be recognised for their other contributions.
Regarding the certification process, I don't agree that anyone should be just "grandfathered" in. Any of the people that have a great deal of knowledge and experience should be able to just take the exams and be done with it. I find it really easy to take them at events like TechEd. I typically book in for one each morning at 8am and usually it's only $50.
Alternately, I do them in beta where they are free. The biggest hassle I have with doing the beta exams is it requires me to know where I'll be on a particular day in a few months time. I usually haven't got a clue even what city I'll be in that far out, unless there is an event on.
I also question that none of them would get any learning benefit from the process. I often see people that have worked with a product for ten or more years who can't pass an exam on it. Mostly, that's because they use 40% of a product every day and the exam covers aspects of the product they never look at.
One of the reasons I do take the exams is it makes me study the whole product. Using SQL Server as an example, it helps avoid the problem I see where people use SQL Server 2005 or 2008 the same way they used SQL Server 6.5 or 7. I like getting the prep guides and making sure I've covered off all the topics on it. Given I spend so much of my time evangelising topics at the prerelease or early adopter stage, there usually isn't much in the exams that's a surprise by the time the product comes out. After I've covered the material, doing the exam is then almost an afterthought.
However, I don't consider that having done the exam means much at all. You can buy a complete word-for-word copy of the exams for about $30 out of China if all you want to do is just pass the exams. Until this nonsense stops, the fact that someone has done them means almost nothing on its own, unless they took them in the beta phase where no such cheating options are available.
For those that take the exams seriously though, there definitely is value in the preparation process, rather than in actually taking the exam. Once you've done the prep work, you might as well do the exam. An additional benefit is that many people are timeline driven and having an exam booked tends to create a sense of urgency in preparation.