Hi people,

From my point of view, using software to debounce the encoder isn't difficult and takes low resources.
The only reason why I would use extra components should be for ESD protection has many persons mentionned.
However, optocouplers seems cheaper than these components like Agilent or Maxim ones.

So, finally this should depend on the application.
If this is used as a selector for changing values on LCD, the cheaper solution with optocouplers seems good.

If this is used as mechanical position coder on safety devices, well, ... do an FMEA !
According to the result you may decide which solution is good enough.

Stephane