I've done some work on this and what I've done is installed debian on a modest 1024 MB image on which I will store backup tarballs. I can also use this config profile to boot into somewhat of a rescue OS where I can mount my main partitions and restore them from the tarballs.
That being said, I can also download these tarballs and restore them to my very fast home PC, chroot into it (ala "Faketoo"), and then do all my package updates from there. Of course, using this method means you have to actually bring your server down to perform the restore operation, but it usually doesn't take very long and it improves update times exponentially.
Another thing I've done with promising results is to do the Faketoo style restore on my home system and then build binary packages. This way I can just have emerge use the binary package tarballs to perform updates. Doing it this way means you don't have to reboot your server!
Hopefully this will serve to reduce the load on some hosts
Maybe I can work up a HOWTO on the subject
