I received a letter from Bankwest advising that for 6 months, we'll get 1% cashback on all purchases on the Zero credit card. I couldn't find any info on their website so it might be for existing card holders only.
Most reward credit cards are usually around 0.5% cashback (in form of gift vouchers or items, etc) so we'll probably use the Zero card now for 6 months instead of our usual Qantas FF card.
Before you go jumping to a new account, I strongly recommend you take another look at http://www.ozbargain.com.au/node/73866.
In particular, the bit that says "The new scheme, which was introduced in an amendment to the Privacy Act by the Attorney-General, Nicola Roxon, last month, will allow credit reporting agencies to add the following information: the date a credit account was opened; the type of each current credit account (mortgage, credit card, personal loan and so on); the date a credit account was closed; the current limit of each open credit account; and repayment performance history".
This suggests to me that credit agencies will be telling potential lenders, among other things, if you've been changing your credit provider regularly (suggesting that you may be maxing and moving, for instance).