36 percent of active iOS devices are already using iOS 7 according to information published by Mixpanel, a mobile analytics firm.
Apple has frequently touted the rapid adoption of new operating system upgrades as a significant strength of its mobile operating system, ensuring that developers who adopt new APIs and features like iCloud or Passbook will see a large market for their wares.
For one more data point, 44% of visits from iOS devices to MacRumors yesterday were from devices running iOS 7.
Article Link: Multiple Data Sources Suggesting iOS 7 Adoption Rates Well Ahead of iOS 6