iOS 8 adoption is picking up, but not as quickly as its predecessor. According to data released by mobile analytics firm Mixpanel, the adoption rate of Apple's latest mobile operating system stands at around 45 percent as of today, nearly 20 days after it was launched. This compares to iOS 7, which had achieved an adoption rate of around 70 percent over the same period last year.

Mixpanel gets its data from users using its customers' applications. "We work with thousands of apps and that means tens (of millions) to hundreds of millions of users across all kinds of devices", a company spokesperson said last month. Another analytics firm, Fiksu, says the number is actually lower, reporting an adoption rate of only 37 percent for the new OS.

Apple released iOS 8 on September 17, and on September 21, the company revealed that nearly half (around 46 percent) of the devices that connected to the iOS App Store on that day were running its latest mobile OS.

Meanwhile, iPhone 6 adoption rate has skyrocketed; less than three weeks into the launch, the device has touched the 4 percent level. Just to give you an idea, the combined share of iPhone 5 and 5c was around 3 percent over the same period.

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On the other hand, the adoption rate of iPhone 6 Plus stands at around 1 percent, slightly more than that of iPhone 5c.