9p is really easy to implement. That is a key feature as it makes it easy to create new clients and servers (and presumedly makes bugs rarer). Much like FUSE has been adapted to countless things. I don't know how implementing a FUSE server or client compares to this though.
Unfortunately, the simplicity also means giving up something. Where quite-complicated NFSv4 can be very efficient over slow links (leases makes it a bit like a cache coherency protocol), 9p requires all writes to be committed to the server (for coherency).
9p is really easy to implement. That is a key feature as it makes it easy to create new clients and servers (and presumedly makes bugs rarer). Much like FUSE has been adapted to countless things. I don't know how implementing a FUSE server or client compares to this though.
Unfortunately, the simplicity also means giving up something. Where quite-complicated NFSv4 can be very efficient over slow links (leases makes it a bit like a cache coherency protocol), 9p requires all writes to be committed to the server (for coherency).