Just came across this plan on Optus who are offering 140GB for $70 a month on a 12 month contract.
BYO device, free music streaming and you can pool the data with other Optus services on your account. Nearly good enough to replace your home internet plan.
If you are going to get Optus for data or replace home adsl , I would recommend vivid Unlimited for $89 per month with one month free via referral
If you watch Netflix or Foxtel go , 140gb is really not much