I was seriously looking to sign up with ratebusters a few years ago; lucky I didn't.
Because much later I found out on other forums on how rateBusters adjust their variable rate loans.

It seems, according to forum posts, the rate you see on their web site are for new customers only. Once you sign up, you are no longer new customer. So for the first few months, you pay the same rate as 'new customer'. Then after a while, you will be paying slightly higher rate than 'new customer'. As time goes on, you will be paying a lot higher than the 'new customer' rate as shown on their web site.

Just to be clear, the rate rise are nothing to do with reserve bank rate raise. For example, when reserve bank raise by 0.25%, the 'new customer' rate goes up by 0.25%, and the 'old customer' also goes up by 0.25%. But once in a while, 'old customer' rate will go up while the 'new customer' stay the same.

Though I think they may time the increase to coincide with reserve bank raise, so something like 0.25% for new, and 0.35% for old.

Another lender, 'myRate' also do this. You can google it, I found a lot of people complaining on the web.
… maybe safer with big 4. Though I think rate buster and myRate are still cheaper…