From capify,
"Capistrano 2.0 is the first significant update to Capistrano in a year. It represents a major refactoring of the tool's internals, as well as a complete reworking of the deployment recipes."

All you need to do for upgrading your existing Rails app using cap1.x is to,

a. Capify your Rails app,
capify .

b. Not mandatory step:you can easily update those previous deployments to use Capistrano 2's new per-deploy REVISION file:,
cap -f upgrade -f Capfile upgrade:revisions

On first attempt to upgrade I got following error,
subversion.rb:56:in `query_revision': undefined method `[]

resolution to which has been given by Jamis here,

http://www.mail-archive.com/capistrano@googlegroups.com/msg01123.html

From the updates to Capistrano 2.0, I love the feature to have namespaces and event framework for extending tasks.