If you're (like me) using Extension Library in all your XPages applications and therefore you need to install it on all servers your aplications run on, then Plugins Deployment for Domino project is what you'll like a lot. Believe me.
It has some problems, like not being multiplatform - importing updateSite works on Windows only. I tried it on Linux (no luck) a read that it has the same problem on MacOSX. It's probably just the problem of showing the progress bar, I'll look at it later.
Now I am in a stage #1 of moving everything onto my new laptop, so I've got nearly no spare time.