OS X 10.8.2
MBP 13 inch, Early 2011, 4GB RAM
If you connect a comparator's output to one of its B inputs, put it in subtraction mode and power the A input, the output signal starts to pulse rapidly.
This is not a bug, but if you connect this pulsating signal through a repeater into a dispenser, setting different delay times on the repeater causes inconsistent behaviour at the repeater and the connected dispenser.
I talk about this in the following video:
or, if the upload works, i attached the relevant part of that video to this report