>Would using files with the USE ... NOUPDATE clause make access to those files faster in a multi-user network environment?

It did once, back in the time of XT and 286 machines, and generally should work today as well, because it eliminates locking. Those who don't write to a file, don't require locks, and the network has that much less overhead. I don't know how much, though, as a lock is just a few packets travelling between a WS and the file server (request, response) and the server checking somewhere in the file's map whether the lock can be granted or not, and writing an entry when a lock is put (and erasing it when unlocking), plus some signalization about dirty old buffers. But in a tight spot this may help some. YMMV, I guess.