If you'd like to help out testing the new "stateful re-exec" feature of Upstart which we hope to land for Ubuntu Quantal, see the details here:
In brief (more posts will follow), "stateful re-exec" allows Upstart to be restarted (or upgraded!) without rebooting your system. A basic restart or re-exec isn't difficult, but what stateful re-exec does is maintain Upstarts internal state over the re-exec such that it continues to track jobs and log job output.
This is an early cut of the code so don't install it on any critical systems. Additionally, there are some caveats...
... but we plan for that list to dwindle quickly over the coming days and weeks.