If each user has his/her own node, they can set priorities of their
own processes as they wish: If they set one of their processes to
realtime priority, it has that priority only over other processes of
that user, not over processes of other users.
The flip side of this is that if a user renices a process, it will only
make it have a lower priority than the user's other processes, not with
respect to all of the processes in the system, which is what is usually
desired when someone is renicing a process.
- Ted