This is a brand of merged credit unions (mostly old university credit unions).
Looks like there is a $600 application fee, but I haven't confirmed that this applies.
They are advertising the rate that rolls to their higher standard 5.31%
https://www.catalystmoney.com.au/1fixed
But I've seen on their site that for new Home Loans >$250k under their Premium Home Loan Package the roll to rate is 4.35%.
Here's the link for the $1000 cash back (must apply before 31 Oct 2015).
https://www.catalystmoney.com.au/campaigns-campaigns-2015-sw…
Hope this helps and let me know if I should add anything to the post.
5.21% comparison on the 3.5% fixed. No deal there.