Your concept of what is scale looks very different than mine, in my experience NFS does a very good job for in-datacenter workloads. CG rendering, oil/gas and others usually take this approach for HPC as far as I've seen. I consider this "scale". Close to 100k procs sharing the nfs is the biggest cluster I've worked at.

Of course that over longer networks it isn't suitable as the roundtrips have too much latency, other than that, is your experience much different regarding nfs?