For the first time ever, there are more people running a more recent version of Android than 2.3 Gingerbread, according to Android's Developer site. Android 4.0 / Ice Cream Sandwich and 4.1 / 4.2 Jelly Bean posted 28.6% and 16.5% of the market, respectively. That adds up to 45% of all Androids, overtaking Gingerbread's 44.2% take – if only by a smudge.
It's been a long time coming. Ice Cream Sandwich was first launched in late 2011 on the Samsung Galaxy Nexus. The OS took nearly 9 months to reach 10% of all devices. Blame carriers and manufacturers, who have increased fragmentation by taking their sweet time to update phones.
The gulf between Gingerbread and Ice Cream Sandwich is immense, with the latter having a far cleaner, more sophisticated UI, as well as an improved camera, widgets, navigation and notifications. The fact that more people are running Android 4.0 means that finally more people are seeing how great Android can be compared to the competition.
Nobody really likes Gingerbread anymore. The OS is ugly and clunky; a poor replacement for iOS. Today's Android OS is much more powerful and beautiful, and it really stands out from the pack. The fact that more people are using it now means that Android's reputation is likely greatly increasing. You can't use the latest version of Android and not fall in love with it (Gingerbread is, of course, another story...)
Google calculates data relating to OS version by monitoring those devices which have accessed the Google Play store within a 14-day period, so it's always best to take the stats with a grain of salt; those running older devices are sometimes less likely to download apps on a regular basis. That said, the data should be valuable for any app developers who want to create apps that a majority of Android owners will be able to use.
Source: Android Developer's Blog