Time spent in the ready Queue. Consistently bad often considered better than consistently inconsistent. Short jobs get stuck behind long jobs. Avg waiting time is far from optimal. Good throughput, not fair, non-preemptive.
Long jobs starve, requires oracular knowledge, users lie like rugs.
Obviously, run the short job before long one - you get lower waiting times. Moving a short job before a long one decreases the wait time for the short job MORE than it increases the wait time for long one. You lie, you die. If a process has been using the CPU for about 100 ms lately, it will most probably do so the next time also. This concept is important for real scheduling algorithms.