In the US.........
There is nothing mandated by regulation that should be read back EXCEPT hold short clearances. They must be read back verbatim...
However, this is one of my pet PEEVES with US flight crews. About one third of the time they are failing to use call signs with transmissions. The state of US flight crew phraseology is getting worse by the year it approves and is making our jobs HARDER! We have to continue to restate the clearance and they piss off the flight crews due to "Yeah we allready SAID that..." Well, if you don't use a call sign we don't know it was YOU! This isn't a telephone... It is a two way radio with more than just yourself up there...
Rant off...
regards
Scott H. Voigt
NATCA Southwest Region
Safety and Technology Chairman