Chris Sauve:

iOS 5 captured approximately 75% of all iOS users in the same amount of time it took Gingerbread to get 4% of all Android users. Even more astounding is that 15 weeks after launch iOS 4 was at 70% and iOS 5 was at 60% while Ice Cream Sandwich got to just 1% share at the same age. If there were any question as to whether iOS had a less fragmented ecosystem than Android, the past two charts provide a fairly definitive answer.

But Android is winning.