Running the iozone program on a nfs mounted volume, linux client IBM RS6000 as the server, the performance on write is about 15KB/s for a 10MB file with an 8K buffer size. On a freebsd 228 system from the same mount point, on the same network subnet, 10MB/s ethernet, the average is about 800KB/s to 1MB/s. Any other network transfers, ie ftp, rcp... occur with the expected performance of 700KB/s and 850KB/s. This problem seems to be very localized to the NFS client implementation.
NFS performance is a kernel issue and is being addressed in the upcoming new 2.2 kernel versions. We will undoubtly be including 2.2 in upcoming releases.