the price drop of the galaxy makes it the best pic of the bunch. it's also rumoured to be getting honeycomb (android 3.0). wouldn't bother with the optus or telstra tabs (and probably any other cheap ones) because of the screens.
to be honest though, i'd look at a netbook. i picked up an acer netbook from officeworks for $359. it's a dual core 1.5ghz with 1gb of ram (can upgrade to 2gb). it has good battery life (can surf the net for 6 or 7 hours). you get the advantage of having a keyboard, faster processor, will do pretty much anything a normal laptop will do, and being windows 7, my ps3 auto detects it as a media server so i can stream movies and music to my ps3 without having to go through any settings, as well as link to my windows 7 laptop to share data very easily. plus you can plug in USB devices. only thing is that you would need a USB dongle for mobile internet (or a phone with tethering abilities, such as an android phone running 2.2 or an iphone). it also runs android dual boot, but you can't add apps to it, but it is good for quickly loading up to search the net or send an email (boots up in 10 or 15 seconds).
this is the one i got (missus picked the colour)
http://www.officeworks.com.au/retail/products/Technology/Computers-and-Notebooks/Computer-Notebooks-and-Laptops/ACN55DQPK