On a need-to-know basis 

• Other Watchers (idle,var,timer,io,signal)

• Watchers can generally be messed with during program execution (by setting attribues)

• Object management done for you (all_watchers(),all_running(),all_idle())

• Schedule is defined by a bunch of priority-ordered queues

• There is some fairly complex flow-control options available (loop(),unloop(),unloop_all(),sweep(),one_event())