I just purchased a $50 starter pack for my Son on special for $30.
When I ported across from Boost, I got 10.5GB and 28 days on the Combo, but when we checked it a couple of days later it had changed to 20GB and 56 day expiry. I couldn't see the 20gb offer in store but when I called up, I found out you can get if you port in.
He mostly uses Wifi but for $30 I'm thinking of using it as backup for my Adsl modem as well.
Here's a screenshot of My Vodafone screen.
http://imgur.com/a/EcAxI
Did this yesterday and it worked. Double data thing does take 24 hours to tp come on to to the phone but works.