I'm writing about how Ubuntu handled an automatic update the week of March 5, 2007. These days the process of keeping your system up to date has evolved considerably so that it is very easy to stay current with fixes and security updates.
Read the blog entry here
Linux distributions have also had upgrade issues along the way. In Ubuntu's case there is the notable failure during an upgrade of xorg.core in Ubuntu 6.06 that broke the X desktop. The disruption was limited in scope and a solution quickly provided. I've not heard or read of anything of that magnitude since. But the ghost of that incident was briefly resurrected last week when I attempted to update a number of packages, three of them related to the X windowing system.