So, I wandered in this morning to find my local profile, registry, etc purged and I had to set up, install and configure EVERYTHING all over again :( that being said Firefox had a little surprise for me, it doesn't seem to store anything in the registry. All my settings, bookmarks, plug-ins etc were all installed and configured the way I like.
Awesome!
registry, no but it does store all its settings in your user folder under neath the application data folder.
I suspect that they split up some of your roaming profile on different servers.