Anyone using it gets A$25 (about US$20) back after the accommodation has been used. So far three have taken the offer up and should each get A$25 back after the November Hobart Unconvention.
This is not restricted though to only attendees of the Hobart Unconvention. Anyone can use it, and we both will get (according to Booking. com) A$25 back after we have stayed in the booked accommodation.
I'm not sure if this offer is only for Australia, or worldwide, and if only for new users of Booking.com. But feel free to give this a go.
I can have up to ten referrals. I have three so far.