In Melbourne, they often talk about “four seasons in a day” and given the weather the first few days of the tournament one can understand why!  The big issue is that because there are roofs over the two main stadium courts, there have been two different playing scenarios on the super hot days and during the rainy moments, i.e. stadium matches continue under the roof in Rod Laver and Vodafone Arenas, while other courts are suspended.  The extreme heat rule is in effect and has already been implemented because of searing temperatures on the first couple days of the tournament.  Of course, there was the Maria Sharapova first round match which continued outdoors without the roof closed in excessive heat simply because it had started under those conditions.   They also have the Hawkeye instant replay electronic line calling system in place at the 2007 Australian Open, but it is only being used on the Rod Laver stadium court.  Therefore, it has become in a sense two different tournaments or at least two different sets of playing conditions, i.e. one for the top players who usually only compete on the stadium courts and a second for everyone else.  Is that really fair?  How does it compare to tournament situations where weather forces some players to complete two matches in a day or play a match on a different surface?