I think you struck on an important point. For clients Wordpress is a godsend. If you quit contracting or the client needs to change developers for one of a thousand reasons there's a massive pool of talent that can step right in and make adjustments. I've taken over Wordpress sites and the learning curve is almost flat (save a few weird plugins). Anyways, it's a whole lot better of a situation for clients, developers and productivity in general than the days when everyone had a custom framework that solved the same basic CMS issue.

Yeah, been working with it for quiet some time on and off and still regularly need to search to find out where a function may be being called from.

Is there another CMS that has the same featureset and the same extensibility? I've tried a few, but keep coming back to Wordpress, even though it is annoying and a resource hog. It's too easy to extend, and it has most of the stuff I need built in to the core (as of 3.0 at least). I wish there were an alternative platform that ran on Python and Sqlite with the same polish in terms of features and ease-of-use, but I haven't found one yet (correct me if I'm wrong!)