Thirty-eight percent of iPhone owners have already updated their handsets to run iOS 5, compared to 30 percent of iPad owners and 12 percent of iPod touch owners.
That's according to a report from market research firm Chitika Insights, which analysed iOS traffic from 22 to 28 October.
While 37.7 percent of iPhone owners are running iOS 5, the majority - 58.7 percent - are still running iOS 4. Just 3.2 percent are using iOS 3 still.
However, more than twice as high a proportion of iPod touch owners - 8.8 percent - still run iOS 3. That's not far behind the 12.2 percent running iOS 5, though most iPod touch owners are using iOS 4.
"Evidently those using the iPod aren't interested in upgrading to the latest software, most likely because their iPod's are mainly used for media or on the go purposes," said Chitika's Gabe Donnini.
Owners of the iPad were more likely that iPod touch owners to be running iOS 5, with 30.3 percent having already made the upgrade. Some 6.5 percent were still using iOS 3, while most - 63.2 percent - were running iOS 4.
"While the iPad is functionally similar to the iPod, consumers appear to truly care about having the latest software. This could be attributed to iPad users desire for greater utility and have a more frequent and open interaction with the device's UI," Donnini said.
"It's difficult to make statements about a specific market. Just by looking at this data sample, one might think that iPhone and iPad users are innovators or early adopters; however there is considerable overlap across Apple's product lines. Apple users are known for their loyalty, and many are guilty of owning multiple devices."