the only thing that bugs me is that sometimes typos are counted as wrong, and sometimes they are accepted.
It is not always easy to tell if you made a typo or a mistake, but Duolingo is developing; maybe some day it will accept more typos and other little failures made because of inattention.
I know that losing hearts because of typos is annoying, but try to shift your attitude a little: when Duolingo does not accept your typo, it is not a punishment - rather, when it does accept it, it is a little gift. If you manage to think this way, you'll be a little happier with your experience. Who knows, maybe you'll even learn to make less typos in general thanks to Duolingo :-)