The most controversial thing in the IPL 6 was the match/spot fixing allegations against some of the players and the owners. Several players including Sreesanth was arrested and some of them were banned. Anyway with all these allegations it seems that the final report of the scandal is released to the SC of India. (http://www.espncricinfo.com/india/content/current/story/795559.html)
It will be interesting to see what actions will be taken against the players, team owners and others who are involved in match fixing. As BCCI is the ultimate controller of Cricket in the whole world, due to their financial strength, it will be very interesting to see the impact on World Cricket.