Given its overall size, it was surely only a matter of time before iiNet added mobile telephony to its roster. The ISP has added a set of postpaid mobile options to its roster, but doesn't currently have any prepaid plans.
There are three monthly plans: $10 (200MB of data and $150 in call credits), $20 (500MB and $400) and $40 (1.5Gb and $750). Rates are standard and unremarkable: a 35 cent flag fall, 90 cents a minute for cells, and 25 cents for text. The plans are described by iiNet as "contract free", though you'll need to be an iiNet customer to sign up.
Like practically everyone who doesn't own their own mobile network, iiNet is using Optus for its service. That means you get some familiar Optus features (free browsing on social networking sites), and also potentially Optus' network performance woes.