I'm a Guest Services Manager for Virgin Blue, and our policy does not allow Car Seats on the aircraft, but you can take your pram with you up until boarding time and the crew will check it in from there.
That is interesting. We flew back from Cairns yesterday on VB. I saw that Qantas do loan strollers to use within the airport and asked if VB do the same. The reply I got was "we don't do that". At no time were we told we could take our pram into the departure lounge and then would be checked in when we board. I will definitely be doing this in future especially as DS is getting too heavy to carry.