I agree with Spuds, till I came O/S I had practically never heard controllers use the phrase expedite climb/descent. It was saved for the time when you really need it cos someone has screwed up. Over here (Middle East) there are guys who use it 3 or 4 times a shift, and basically expect the pilots every time used to give them a very good rate of climb. My problem with that is the old "Boy crying wolf" mentality. If a pilot gets told to expedite climb every other day, they will start to go "yeh whatever", whereas one day I might really need a guy to squeeze everything out and help me out, and he won't realise this. If I say expedite, I am expecting that within safe levels, you will give me your maximum rate of climb or descent. If I simply want a good rate, I will ask the pilot can they maintain for example, 1,500 ft per minute, if so fine, I will work on that.