According to Chitika, most iOS users are running either iOS 7.0.3, which accounts for 59.1% of iPhones and 56.4% of iPads, or iOS 7.0.2 which is running on 24.2% of iPhones and 27.1% of iPads. Very few users had updated to the latest version of iOS 7.0.4, which was on just 3.3% of iPhones and 2.7% of iPads. iOS 7.0.1 is the bottom of the barrel with 0.3% of iPhones and no iPads. And, 13.1% of iPhone users and 13.9% of iPad users are still running plain old iOS 7, without updating for any of the bug fix/security updates.
It is quite interesting to see this more granular data on the iOS ecosystem, because usually all we see are the basic numbers for how many users are running the "newest" iOS version, which usually includes all incremental updates. Just because an update is available, and it is easy to install doesn't necessarily mean that users are updating.