I've been doing live upgrades on Debian (and now Ubuntu) systems since, well, 1997. It's always pretty easy and straight forward.
Why, 10 years later, do the RPM based distributions still recommend you boot from CD/DVD to do an upgrade?
I've upgraded hundreds of Debian and Ubuntu boxes with very few problems. Apt, Deselect and DPKG just take care of most of the details, and now Ubuntu has packages to make it even easier. What the hell makes this so hard for the RedHat's of the world? They still even suggest a full reinstall is the best option.
Just when I've gotten used to the suckyness of yum, setup my package building infrastructure and about happy with CentOS, this has to rear it's ugly head again. Yeah, I could try to contribute something to fix this, sure. Or wait for some of the new RPM projects to make it better. Or, I could go use a deb based distribution and have this shit just work, like it has for the last 10 years.