It takes 1.5 ticks (0.15 seconds) for a piston to extend/retract. While the piston is extending or retracting the block that it is pushing immediately turns in to a "move block" (id: 36) during those 1.5 ticks. This moveblock doesn't conduct redstone power, it works like glass. There for if a solid block is moved it immediately blocks signals from repeater or torches, and releases signals from wires the solid block was blocking.
Using this we can make Logic gates that function instantly.
[Pictures and descriptions will be added at a later date]