On the day of their announcement, Cloudbees provided an FAQ and a Migration Guide for their current customers.
In addition, Heroku most considerately have a CloudBees-to-Heroku migration guide (updated on the day of the CloudBees announcement, nice).
Setting up on Heroku proved delightfully simple, and with a git push heroku master from my machine, my first app was "migrated". Up and running, and actually (according to my simple metrics) responding more quickly than when it was hosted on CloudBees. Epic win, amirite?
Well, not entirely. The git push deploy method is all very well, but I dislike the implied trust it puts in the "pusher". How does anybody know what is in that push? Does it pass the tests? Does it even compile? When CloudBees was my end-to-end platform, I had the whole CI/CD chain thing happening so only verified, test-passing code actually made it through the gate. But Heroku doesn't offer such a thing - they just run what you push to them.
Oh dear. CloudBees are no longer offering a free Jenkins service.
Back to the drawing-board!