I still use an old 3G dongle during long train commutes but it would be nice it it was faster (actually a ZTE/Telstra NextG MF6261).
I sometimes change networks on it, so it helps to be unlockable, and would help if it support Telstra/Optus/Voda 4G bands or at least some of them.
I currently use Optus prepaid data and it is adequate on 3g.
A small form factor is helpful, and the ZTE has a folding plug that was also good for keeping the device out of the way when in use. And I use it on a macbook air with no front end software, so mac drivers would be good.
What can OzBargain recommend?