Go and pick up a copy of Australian Property Investor magazine. You can get previous copies and they had a couple of issues at the end of 2007 where they were picking the best suburbs and giving reasons.
I like Cammeray but only because I stayed there for a few months and appreciated the easy access to the city as well as the green feel to the suburb. I don't know Sydney well enough to comment beyond that other than to say if you can buy along the North Shore rail line you can't go wrong, that was a tip that a long term Sydney investor gave me.
