If they can do a cheap but cheerful - first flight of the day, last flight back home pattern to Sydney, and even Melbourne, then I would a take a serious look at it for our business travel. I'm quite jealous of the Jetstar deals that the rest of Australia get to access - if REX can fill that void, I would be grateful.
I think they would also pick up some of the leisure market to Canberra, where people want to travel here on the weekends for the blockbuster events at the National Museum and Gallery. Qantas have priced themselves right out of that market.