Hey Ausatco, When I worked an extremely large non radar sector in Oz, a few years back, I heard a couple of the asian pilots use CC. Now over in the Middle East, I hear it alot. It isn't any quicker than "affirm", but it is clear what is intended by the response so I have no problem with it being used. Generally Australia is, from what I have seen in a very multicultural ATC Centre here, the most regimented and strict RT wise, and sticks to the book more than anyone else I have seen. Initially coming here the relaxed RT freaked me out, and I fought against it, but you hit your head against a brick wall long enough, you just give yourself a sore head. Once you get over that, the relaxed RT generally works just as well, and I think Oz could learn a bit from the rest of the world and take a chill pill.
I still remember the look I got when I "concurred" to a level change. The other controller was sure I was a horses hoof!!!