It depends what you are looking for. HK is great if you like being on the go all the time and don't mind high density living. The expat lifestyle is work hard, play hard. One thing also is that they stick together and look out for each other, because most of the time, family is miles away. The local population there though, you may not find as affectionate but they do compensate by the flavours that they feed you :P
I am originally from Perth, and I now live in Sydney. I lived in HK for a few years when I was a teen cause the folks moved over. I love the wide open space and the culture in Perth but I love the professionalism and nightlife that Sydney offers. Saying that, and with reference to high density living, I recently moved into a block of Meriton apartments just on the outskirts of the cbd, and I am already looking for a new place to move again to. I guess relative to the size and the pace of the city, apartment living just doesn't go down well with me here whereas in HK it is part of the excitement.
I'm in my mid twenties and definately plan on doing a stint in HK in the next couple of years.
It's a fantastic playground and is one of the best gateways to what you plan to achieve.