I host a number of Joomla! websites. Most of them are 1.5, though I still have a client that is on the 1.0.x branch. (Tell me about it!) None of the extensions are up to date.
I also host a number of WordPress blogs. All of them, as well as the installed plugins, are all up to date to the most recent release.
Over the last couple years of keeping Joomla! & WordPress installs updated, I have gotten to the point where I was about to stop hosting Joomla! installs, as I still have to manually upload & update both the core files & the extensions. WordPress has had this feature since December 2008! (Since version 2.7)
With the ever-increasing mass hacks made possible by vulnerable, out of date Joomla! plugins + absent ability to easily keep those plugins updated, I was about to toss in the towel for Joomla!, and declare it too much of a risk to run on my server, when I noticed that the recently released Joomla! 1.6 finally adds this much needed feature of automagically finding core & plugin updates & installing them–The catch of course is that the plugin developers have to setup their plugin to allow this.
So yes, there is hope for all you Joomla! fans out there, though the fact that it took them so long to add this feature is quite disconcerting to say the least…