I often get asked which is the better Exchange certification to pursue for someone who wants to work as an Exchange administrator or consultant. The natural inclination is to the latest version, and in many cases this would be fine because learning the latest version of a Microsoft product teachs you many things about previous versions as well.
Exchange Server 2007 is an exception though (in my opinion). Exchange 2007 is far more than “Everything in Exchange 2003 plus new stuff” and is vastly different from any previous version of Exchange. And many organisations still run Exchange 2000 or 2003 in their environment.
That is why I always recommend pursuing both certifications for someone keen to work with Exchange. This is based on my experience over the last couple of years working on Exchange 2007 projects. At least 90% of these projects involves migrating from either Exchange 2000 to 2003 (one was even 5.5!), with only a small number being a complete “greenfield” installation of Exchange Server 2007.
Now you could certainly skip Exchange 2003 certification if you know you are only going to work with Exchange 2007, but if you want to set yourself up to be more employable when it comes to Exchange skills then certification in both 2003 and 2007 would be an advantage.
If you want to know more about pursuing Exchange 2007 certification check out my post on the essential Exchange 2007 toolkit where I list some documentation and training resources that are very helpful.