Since its launch over three months ago KitKat hasn't made much of an impact. It has now overtaken Froyo is terms of the number of devices using it - but only by half a percent.
The Dashboards on the Android Developer site provide information about which devices are active in the Android and Google Play ecosystem, which means it is restricted to Android 2.2 and higher. The latest figures show that Jelly Bean, Android 4.1 through Android 4.3, is the firm favorite with a total of 60.7%, while Android 4.4, KitKat, has only a negligible share - 1.8%.
Take up of new Android versions has often been slow, but KitKat might face more problems than some of its predecessors. Despite being a decimal point upgrade, Jelly Bean introduced major changes and brought with it a smoother UI which was highly desirable.
KitKat, Android 4.4, was another decimal point upgrade and there were few changes to the core OS although it did introduce three new frameworks, for printing, storage access and HCE - NFC Host Card Emulation, an attempt to revitalize Google Wallet .
Another feature was the introduction of Google Play Services 4.0 and this may in fact account for its slow uptake. Although KitKat brought with it the Nexus 5 phone, it may be that phone manufacturers don't fancy getting too embroiled into the Google ecosystem and are reluctant to follow Google down a path that gives it more power. On the other hand it could just be the usual sloth that typifies the way phone manufacturers upgrade their OS.
The bottom line is that for most users KitKat isn't sufficiently different from Jelly Bean to cause them to rise up and complain that they don't have it - its nice but mostly not essential.