upstart is not stable yet?

I know almost nothing about upstart except that it has replaced sysvinit on ubuntu, I don't understand how it works and the man pages, while providing copious details, aren't helping me get oriented to this new system. Searching for information, I soon came across https://bugs.launchpad.net/ubuntu/+source/upstart/+bug/557177, which I found quite off-putting. So much so that I thought of reverting from Ubuntu (which I have been enjoying in many ways) to a RH/Fedora release, until I read post #40 on that bug thread. So, I decided to try a little harder to learn upstart.

Next I found http://upstart.ubuntu.com/ and after a few seconds was reading http://upstart.ubuntu.com/getting-started.html. There I was disappointed to read "Note that the job file format is not stable yet, so if you upgrade upstart later, you may need to fix existing files."

What I want to know is whether this comment is still a correct description of upstart, or is it an out of date comment overdue for removal? I don't want to be running systems in fear that every time I update I might break something so core to the system as the startup scripts. I don't really have time to learn it in the first place, much less follow it as it evolves through it's "not stable yet" phase and keep re-writing job files and re-learning how it works.

I appreciate that there are limitations and faults to sysvinit, and the initiative to develop a replacement that overcomes some of these faults. But two of the virtues of sysvinit are its simplicity - it is both well documented and easy to understand what is happening, and it's stability - scripts I wrote many years ago still work just fine today.

People that know better than me obviously see merit in upstart. But I wonder at the acceptance of unstable software for such a critical role.