I don't feel qualified to answer your question, but seeing as nobody else is...
Melbourne has a lot of technology meet-ups. Twitter meetups happen at least monthly, and there are also mobile tech meetups, social media meetups, The Hive for entrepreneurial talks and the like, and regular meetups for [programming language of your choice]. Sydney has a lot of similar things happening, but I'm not as familiar with the scene as I'm not there.
In terms of startup scenes we have a long way to go to match the US. Sydney and Melbourne have a friendly rivalry going -- Sydney likes to think they're more Silicon Valley-like, and Melbourne beg to differ ;) Both have good, albeit small, groups of enthusiastic hackers trying to create a tighter-knit startup culture.
This Melbourne meetup is one of the things we're doing here to try and bring everyone together and get more of a community happening.
One of the other things everyone mentions is how much harder it is to get VC funding in Aus, which is one of the reasons the startup culture is a little stifled.
How are the startup scenes in Melbourne and Sydney?
Are they startup up friendly cities? Is the technology meet-up phenomenon present there as it is in the States?
(All this talk of sunshine has rekindled my desire to get out of Chicago before winter comes...)