as a person who has spent the last three years exclusively in user-level filesystems on Linux, I can safely say this -- my biggest problem during that time has been the root user. from dealing with programs which allow only root-level access (xen tools) to dealing with programs who explicitly disallow root (PBS/torque) much more of my time has been spent twiddling with permissions, sudo config scripts and everything else involving root than actually writing the synthetic user-level file system and getting it running.
it appears that every cluster of programs used to do anything systems-y in Linux has a special view of uid 0 -- some revere it, others fear it, but no two treat it the same way. only one piece of software said "chgrp my device file to whoever you want to use it and be free". it felt very Plan9-ey.
