Dodo is one of the handful of companies which offers an unlimited ADSL2+ broadband service, but one of its main issues is that you could only get it bundled with a Dodo home phone service, for which the rates were (and are) fairly uncompetitive. Dodo is now offering the unlimited broadband package on its own with no bundling requirement in selected locations. That makes a cheaper deal, but it's still not necessarily a good choice.
You can only find out if you're eligible for the no-bundle deal by entering your phone number into Dodo's site (though metro locations seem the main target). Assuming you are, then $39.90 for effectively unlimited internet might sound like an appealing deal, but there's some important caveats.
As a quick search around Lifehacker, Whirlpool, the TIO site or the web in general will reveal, Dodo has a pretty poor reputation when it comes to customer service. Having an unlimited option isn't much help if there are problems it takes an age to fix. You're also on a 24-month contract, which limits your flexibility.
More importantly, Dodo throttles your connection if you're using any kind of BitTorrent client or other peer-to-peer activity. Realistically, most people who are using hundreds of gigabytes a month are doing so because of torrenting. If you fall into that category, Dodo is a poor choice.
We noted yesterday that the average Australian only uses 6GB a month, but in the comments to that post some readers said they consumed hundreds of gigabytes by watching hi-def streaming video. If you fall into that category and don't care about torrenting, the Dodo offer might be worth considering, I suppose. But think very carefully before you commit.