That's the plan, to have the clients run in pull mode, with the exception of mine, which I will manually push to the server after I've made changes. I have to shut the content server down before doing the sync so the metadata.db can be overwritten.
So far, I've been using FreeFileSync (
http://freefilesync.sourceforge.net/), which isn't quite what I was looking for, but it's getting the job done, and has a helper tool which will watch a folder for changes and perform a sync if I opt to automate it further.
I like the idea of hooking into the calibre startup. I have to see how often the library will change. Right now, it's changing alot, since I'm still cleaning up and adding/removing things. I suspect once it settles down, it might not be worth doing a scan at each startup on the clients.