Take a look at iBurst too:
http://www.iburst.com.au
Service is around $30/month for unlimited access, and coverage is available throughout SYD, BNE, MEL, CBR, and some other areas of Australia.
They've also got a PC-Card wireless modem (which unwired doesn't seem to have):
http://www.iburst.com.au/?deviceoffe...isit&appCode=&
I use it inside an office building at the SYD airport, and it works quite well.
-Merrick