I will always double-check an A/C's cleared altitude in one form or another.
If an A/C comes over and states his cleared altitude (as a requirement in every country that I have worked in) then all is good.
If they do not tell me their cleared ALT then I will make a point of confirming it.
"Dog control, ABC passing 15500'"
"ABC, Dog control, roger, climbing to FL240"
It is on the tape, the cleared altitude has been stated, there is plenty of opportunity to pick-up any incorrect altitudes and fix them.
At the end of the day, one of us will say the cleared ALT, butt covered, everybody happy
