With kind permission of S&R I have uploaded the migration script that we used to upgrade aiesec from ACES to .LRN - an installation with 100000 users and 4000 communities and a bunch of content.
Starting with the migration scripts from sloan this adds a framework for running tasks in parallel that depend on each other, so you can say A must be finished before B can start, but C can start right away and so on. The tasks are started automatically without web interaction, and they are suited for long running processes that must automatically be resumed after server restart. Maybe this is useful for someone outside of data migration as well.
Of course it's highly customized and not well documented, so considerable effort is propably needed to make it work for something else than migration of aiesec data.