N4BB have posted a video of the 10.2.1 call screen in action:-
BlackBerry 10.2.1 brings a completely revamped call screen. The original call screen on BlackBerry 10 had you swiping up to decline a call and swiping down to answer a call.
Apparently, users were experiencing such a difficulty in understanding how to answer calls that it generated a significant blowback. Thus, BlackBerry addressed the issue with this new call screen.
Instead of being in the middle of the screen, the swipe bar to answer or decline a call is positioned at the very bottom.