Pistons can take between 2 to 3 ticks to completely extend and retract when receiving a 1 tick pulse. This can effect many different creations and has to my knowledge existed for awhile. This means that sensitive or precise circuits circuits, Tflipflops, and flying machines to name a few can become much larger, slower or unreliable. A bug report has already been made mentioning this issue that is as yet unresolved however it did not go into detail of the problem.