Alex Barret at SearchServerVirtualization wrote a great piece recently highlighting the momentum towards NFS for virtualization deployments. See VMware shops eye NFS and NAS for VMDK storage.
It is interesting that we've seen two major shifts recently around NFS. One is Oracle's release of 11g and the Direct NFS capability. Another is VMware's improved support for NFS in the latest version of ESX.
Both of these companies appear to be telling customers, "feel free to use any type of client you like...Windows, Linux, doesn't matter. But if we are going to scale the Network Attached Storage infrastructure, we'll handle that with NFS."