Ratebusters?  Avoid them like the plague.  As others have observed, the advertised rate applies only to new customers: after you've been with them a couple of months, they increase your interest rate (significantly over and above RBA increases) so that there is no connection between the advertised rate and the rate you're paying. 

When challenged about this, their attitude is one of absolute contempt – indeed, they seemed amused about it all – and said, "if you're not happy, then leave."  But, and it is a big "but", the exit fees are outrageous, so they effectively have you locked in for 5 years.

Give Ratebusters a big miss.  There are other, better alternatives out there.