This is what Ziauddin Sardar, a respected Islamic intellectual, has to say on the matter (bolding by me):
"Then followed his marriage to Aisha, which is seen as the most contentious. Aisha, daughter of his closest friend Abu Bakr, was only six. But the marriage was not consumated, and the Prophet lived separately from her, until she came of age, many years later after the hijra. And Aisha, one of the most articulate and open-minded women of early Islamic history, was more than happy with the union.
I hope this explains everything.
*excerpt from What Do Muslims Believe, Granta Books, London, 2006
The following quote from Tabari explains why Muhhamad didnt consumate his marriage with Aisha
The Prophet left us and his daughters behind when he emigrated to Medina. Having arrived at Medina, he sent Zayd b. Harithah and his client Abu Rafi? for us. He gave them two camels and 500 dirhams he had taken from Abu Bakr to buy [other] beasts they needed. Abu Bakr sent with them ?Abdallah b. Urayqit al-Dili, with two or three camels. He wrote to [his son] ?Abdallah b. Abi Bakr to take his wife Umm Ruman, together with me and my sister Asma?, al-Zubayr?s wife, [and leave for Medina]. They all left [Medina] together, and when they arrived at Qudayd Zayd b. Harithah bought three camels with those 500 dirhams. All of them then entered Mecca, where they met Talhah b. ?Ubaydallah on his way to leave town, together with Abu Bakr?s family. So we all left: Zayd b. Harithah, Abu Rafi?, Fatimah, Umm Kulthum, and Sawdah bt. Zam?ah. Ayd mounted Umm Ayman and [his son] Usamah b. Zayd on a riding beast; ?Abdallah b. Abi Bakr took Umm Ruman and his two sisters, and Talhah b. ?Ubaydallah came [too]. We all went together, and when we reached Bayd in Tamanni my camel broke loose. I was sitting in the litter together with my mother, and she started exclaiming "Alas, my daughter, alas [you] bride"; then they caught up with our camel, after it had safely descended the Lift. We then arrived at Medina, and I stayed with Abu Bakr?s children, and [Abu Bakr] went to the Prophet. The latter was then busy building the mosque and our homes around it, where he [later] housed his wives. We stayed in Abu Bakr?s house for a few days; then Abu Bakr asked [the Prophet] "O Messenger of God, what prevents you from consummating the marriage with your wife?" The Prophet said "The bridal gift (sadaq)." Abu Bakr gave him the bridal gift, twelve and a half ounces [of gold], and the Prophet sent for us. He consummated our marriage in my house, the one where I live now and where he passed away. (The History of Al-Tabari: Biographies of the Prophet?s Companions and Their Successors, translated by Ella Landau-Tasseron [State University of New York Press, Albany 1998], Volume XXXIX, pp. 171-173)
So Abu Bakr's inability to give him bridal gift was preventing Muhhamad from consumating his marriage with Aisha and not because Muhhamad wanted her to reach puberty! This is the typical lie that muslims love to tell but the quote from Tabari makes it clear that its not so. The other argument is 9 is still young and not the right age.IF he really wanted her to reach adulthood he should have not consummated the marriage when she was 9 .HE could have waited for some more years to go by.