In no particular order, things I have found different with Precise 12.04 compared with previous versions:
- idmapd has changed the location of the Pipefs-Directory. If your uid is generic, and name resolution doesn't seem to work when using NFS4 on Precise, make sure your Pipefs-Directory is set to:
Pipefs-Directory = /run/rpc_pipefs
It used to be
Pipefs-Directory = /var/lib/nfs/rpc_pipefs
More as I find them!