After some nasty refactoring of both the dock and general plugin handling code, and a brief time with no computer access, I'm back to making progress. :-)
I've posted a screenie of the dock-in-progress so you can see what I've been working on, although a static screenshot doesn't do the icon zooming justice. Currently, the dock *does* launch apps and folders, although it doesn't do it "properly" - e.g. using startup-notification, and it doesn't correctly detect if there are currently running copies of dock items.
It supports icon zooming with multiple segments with or without segment labels. Each segment can even have a completely different background, outline, font, whatever, as determined by the theme.
I've also posted up my current to-do list in a tracker, so there'll be a bit more feedback about where I am and what I'm doing.
Once I get the GUI setup done, I'll likely post an extremely pre-pre-pre-alpha version so people can actually download and use this thing :-)