I met nearly all my non-coworker tech buddies there. I ended up adopting Atlassian products, befriending Atlassian staff, and nowadays I tell all new tech acquaintances to meet me there.
Now that I think of it, this is the very exact formula they followed to establish their offices as a tech hub, whether they know it or not.
But they are not the only game in town. Fishburners runs a smooth but very ambitious coworking/incubation space, and General Assembly does tech education & training exceptionally well with some of the most talented people around.
It's almost impossible to launch a tech startup in Sydney without having a foot in one of those places. And in our case, all three.