You see this is where my problem comes in - the unlock screen, "Swipe to unlock" and being left-handed I naturally swipe my thumb to the left where nothing happens (same for swipe to answer calls etc etc). I never even noticed this in iOS 6 due to the obvious slider. This is also if I ignore the ^ arrow that sits below the swipe text of course. 4 days in and I still do this from time to time, I think either indicate a direction or make swipes of both directions work. Seems simple enough but it's something I never had to get used to before...
But since swiping right has been the iPhone standard for so many years, I'm confused as to how this is even an issue. Unlocking my phone is so ingrained into my brain that I barely even look at it. By body just knows what to do by habit. So to me, that's pretty bizarre that you consider that a problem.
Anyway, as for the lack of an arrow slider... I think the glistening text muses up for that. It shows you which way to slide.