Great post! In my own experience of working with NFS version 4 servers, we discovered several bugs that have been actually fixed in latest version of kernels. The unfortunate thing is that most enterprises still run old CentOS / Redhat release kernels that although are stable, but yet lack several of these fixes.
I don't have a lot of experience with NFS aside from a few machines that don't see insane use, but it's surprising to me how v4 implementations seem to introduce such instability. I had an experience a few years ago with a Mac client, quitting vim would cause a kernel panic. NFS v3 did fine.
