We've had bad luck travelling short haul Qantas on a B737 (business) with carry on baggage. Indeed QF has this ridiculous 7kg limit which pretty much eliminates any normal sized carry ons. Around Australia, the business circuit seems to carry around these small rollie bags that are half the regular size and look a little fairy like.
We had a talking to from one FA on the outbound and I had my bag politely revoked from me at business check in on the inbound. I was travelling with a rollie and a laptop bag attached. Again this was business class. . .
Your mileage may vary on long haul flights but I wasn't too impressed on the short haul treatment.