They did have significant distinguishing features previously, specifically their Nokia-specific apps like Nokia Drive and Nokia Transit. Drive for one, I speculate, drove a lot of adoption for Nokia within the WP market. It has received several favorable mentions even on HN, and personally I find it better than either Google's or Bing's navigation apps.

However, that strategy seems to have changed, with Drive being licensed to all Windows Phone devices, regardless of manufacturer. So they do lose a major differentiating feature, but they gain something else: the ability to make money on any WP device sold. I guess they prefer to differentiate on hardware going forward.