i have seen that repeater's and comparator's are very slow at updating.
For example, when you make a repeater-clock with a testfor with a comparator. The comparator updates about 3 second's later. and the repeater clock is also veryslow at updating, and to make the stop bugging for just a but time i have to quit minecraft and re-open it Again. Its not even everytime it helps. But when it does help it only does it for about 5-10 minutes. wich is really bad. also the reason why I care obut this is because for map-makers and minigame-makers and for regular testing with commandblocks.