In some of its design and native apps, Windows Phone occasionally assumes too much. Take the Calendar app as an example. At launch, swipes between our agenda, day schedule, and so on are horizontal swipes, consistent with navigation in many other apps. When we switch to month view, we have to swipe vertically to see the next or previous month, but there's no visual indicator that this is the case. Someone could go on using this phone for weeks or months before realizing they can see months other than the current one. It's not a life-ruiner, by any means, but the interface doesn't make the availability of more information clear, and it's not alone.The situation with Windows Phone reminds us, fittingly, of the recent Windows 8 Consumer Preview. That has been knocked a bit for making certain crucial access points too subtle; for instance, the hidden start button. Microsoft recently clarified that the Windows 8 release will include a tutorial, but Windows Phone currently doesn't have any kind of intro.
I don't think people will have much difficulty navigating around Windows Phone, and I believe it is just a question of the coolness factor.