It seems that Ubuntu 11.10 server defaults to NFSv4, which probably makes sense.
But I'm having problems with ownership on the clients. Both my server and clients run 11.10 and authentication is done with OpenLDAP (so UID/GID's are consistent).
On the server, I do see the correct persmissions on my home directory: UID/GID 2000.
But on the client, this gets mapped to some none-existing uid:
drwxr-xr-x 13 4294967294 4294967294 4096 2012-01-15 01:18 .