unfs3 is pretty good, but it will probably never be as fast as a kernelspace nfs server; FunFS, on the other hand, is already faster than any NFS, simply because the protocol is optimized for minimum latency and real caching, not cheeseball NFS-style caching.
On the other hand, the unfs3 server is already fully functional with a 54k binary; FunFS is still not fully functional, and it's much bigger (if you count its WvStreams dependency). Statelessness (ie. NFS) obviously gives several advantages, simplicity being a major one, but I wonder if these advantages will be worth the compromises (ie. stupid in-kernel servers vs. bad performance) we have to make?