Actually I'm interested in one part of the original poster's question: the thread oli linked to is about which cms is better, but as someone who has so far just coded my own (rudimentary) cms for each site, I'd be interested to find out who uses their own and who uses other, proprietory systems.
In other words, I suppose, how complex does a site have to be before you stop using a backend you've coded yourself and start using e.g. joomla or whatever?