http://winsupersite.com/mobile-devices/ ... ember-2014
These stats come from AdDuplex, which means the data comes from WinRT (or metro) apps. This doesn't tell us anything about the percentage of Windows 8 users who use metro apps. Only that of those who do, these are the devices they use.
Having said that, the #1 device is the Surface RT (at 9.82%) followed by the Surface 2 (at 2.41%).
I think this proves that MS had the right idea with the Surface line. Whether or not you agree with the direction of Windows 8, the Surface line seems to have encouraged use of the metro environment (which is very good on a touch device, as long as it's not balls-slow, like with Tegra 3).