Installed xubuntu 12.10 from the daily build today. I couldn't get the 4.1.8 guest additions to build because it thinks the headers don't match the running kernel. I noticed there are two different linux-images installed, both the same except one says "extra". There are no "extra" headers but when I typed uname -r I get back the normal 3.5.0-1 kernel and not the "extra" one.

I managed to get things working by installing the 4.1.6 guest additions from the repo but it would be nice to have 4.1.8 running.