In the '60s, '70s, and '80s, many top players didn't play in Melbourne. That has completely changed in the last decade. The Australian Open is now a legitimate, full-fledged Grand Slam that will be close to a sellout every day this year. Next year I believe it will become more like the other Grand Slams, where buying a ticket is a nightmare. The changing temperatures and the heat index can be major players in Australia.
Heat is a bigger factor at the Australian Open than anywhere else.
There can be 14 days of great weather too, but usually there are at least a few days of excruciating heat. One of the big storylines on the men's side continues to be the play of Andre Agassi. I'm always wrong about Agassi. I don't know what he has been doing the last three or four weeks since losing to Sampras at the ATP World Championships, but if he is in the same shape, then he will be a factor all year. It's not an easy tournament for him to win because of the heat.