The new OS data for Android has been released by the Android Developers, and things are starting to change a bit quicker now. The adoption rate of Android 4.0/Ice Cream Sandwich was a bit slow since it was released, but over the past couple of months things have been accelerating. While Gingerbread still covers a vast majority of Android smartphones (with 57.5%), Android 4.0/Ice Cream Sandwich is now on 20.9%. This is an increase of almost 6% in just a month for ICS and a decrease of about 3% for Gingerbread. Jelly Bean saw a small jump as well this month. It went from just .8% when it debuted, to 1.2% this month.
It will be interesting to see how much quicker Jelly Bean gets adopted than ICS, since they are so similar.
Source: AndroidDevelopers
