From 0.2 there hasn't been any signifant changes. 0.3.0.rc2 made some changes to the way a daemon boots, so after updating you'll need to run:
$ rake daemon_kit:upgrade
We recommend running this task on a clean repo, or branch, so you can review the changes using your favourite diff tool.
The "safely" method and logging of backtraces functionality of daemon-kit has now been extracted into a separate gem called 'safely', which is available on github at https://github.com/kennethkalmer/safely.
You now need to add 'safely' to your Gemfile like so:
gem "safely"
And update your environment.rb to no longer configure the safety_net attribute (which has been removed completely and will result in an undefined method exception).
To configure safely, make an initializer with your configuration. Alternatively you generate a new daemon and copy the safely initializer into your current project as a reference.