Rails 3 Migration Guide Anywhere?

Has anyone developed or come across on how to migrate to Rails 3 from
prior releases. I would like an idea of how much work it would be.

O.

This screencast may help you:

http://blog.peepcode.com/tutorials/2010/live-coding-rails-3-upgrade

cheers

Also, there is this guide from Jeremy McAnally, http://www.railsupgradehandbook.com/