Did you ever try to build something from sources placed in Eclipse.org? If your .map file contains just a couple of entries - you're OK, but if there are tens of plug-ins to fetch - the mission becomes really impossible, especially during Eclipse.org server maintenance times. I've wrote a simple Ant task, which shortens the build time twice (at least our Hudson shows so). The Ant task is invoked right after the "getMapFiles" PDE builder task, and does very simple steps:
1. Runs "rsync -az" to synchronize local CVS repository with the remote one.
2. Updates .map file to direct fetch process to the local repository.
What you need:
1. Local CVS repository (I used these steps to setup one).
2. Set-up SSH private/public keys to the Eclipse.org, so "rsync" will work seamlessly.
May be this trick is one of CVS advantages over SVN :)