Although booting over the network would definitely take a bit longer than booting from a directly attached SCSI hard disk, performance should be just fine once the machine has booted, as long as you are not doing very disk-heavy things, like working with large scratch files, video to/from disk, running short of physical RAM and needing to use swap space, etc. Also, for your network, be sure that you are using a switch, not an unswitched hub. The performance difference between a switched vs unswitched hub is very noticeable at 10 Mb/s.
If you take this approach, I suggest taking the extra step of setting up a single, shared home directory, i.e. set up a single NFS share that can be mounted at /usr/people for all systems, providing access to the same personal files and settings on all machines, with no need to duplicate environments. Once you've done that, you have pretty much duplicated a type of IRIX deployment that was widely found in corporate environments and in academic computer labs, circa 1996.
