Mixing Eclipse projects -- getting to where you want to be

Foo Yung Chang commented on my earlier "Fractured Eclipse?" post with a perspective that I hadn't previously considered: "These users don't read newsgroups and post to Bugzilla; they just want to build their database-driven webapp without learning how to operate a nuclear reactor. These tasks reside at the intersection of WTP (75%), DTP (25%) and TPTP (25%)."

I think this calls out the need for cross-project use cases delineating the types of things that users want to do, and the part of eclipse.org projects they need to accomplish these tasks. Callisto is a first step in this area, simply trying to get everyone on the same page, platform-wise, and to see what happens from that. What sorts of cross-project uses cases are out there? Which ones should eclipse.org address, and which ones should be handled by the extender community?