Well that was quick. Just 90 days after Windows Phone 8 became available it has surpassed Windows Phone 7 usage in the US. The two year head start by WP7 was not enough to slow down WP8. This information comes from AdDuplex. They report that WP8 accounts for 50.1% of Windows Phones in the US. This could be because WP7 usage was just that bad, or because WP8 adoption has been that good.
Previous sales numbers indicate that the latter is the case, but dreadful Windows Phone 7 sales have definitely helped. This is a good sign that while Windows Phone 8 is no where near Android and iOS it is still better than previous versions. This should help make developers spend more time on WP8 and help the platform grow instead of wasting time on WP7 (sorry WP7 users). The next goal for Windows Phone will be keeping Blackberry at bay. If their Super Bowl was any indication they are poised to make a big comeback. Microsoft and Windows Phone need to secure the third spot.