The best thing about stack edit, as well any other MarkDown Editor Software are that they provide you with many options to customize your own preferences which could make it more user friendly than some others out there! Although I have not encountered anything major yet but then again i am still using my software for only 2 weeks now so far nothing comes up!! But yes everything seems fine right till this point even though its free version of course we can't expect too much from them since their pricing model kinda expensive compared if when used properly like what Word has done before Microsoft bought theirs over years ago.
So try use at least one or two months first time around because sometimes things may need adjustment especially while creating tutorials etc., You don’t get all those "Power Tools" by just installing such softwares without doing proper testing (atleast) once beforehand. As mentioned above most probably no problem will arise after couple month usage.