Practically speaking

While the practical position of the Orthodox church in regards to non-Orthodox religious persons is one of non-judgment, this does not mean that the details of doctrine and the practices of various groups are unimportant.
As Orthodox, we never say a particular person will NOT go to heaven, for we can never know someone else's heart.  It seems that often we don't even know our own heart, so we should never judge anyone else.
One thing we do say, though, is that the Orthodox church is THE body of Christ.  We know where the Holy Spirit is, we don't know where he is not. 
We can say that various religious groups, as a group, are not valid forms of Christianity, and therefore should not be pursued or acknowledged as Christianity.  But again, we are talking about organizations, not individuals. Is person A part of denomination X? We will say nothing about person A, but we can say that denomination X is not a good place to be.  Although, we do believe that God can and does use a wide variety of situations, often very unusual, to bring someone to himself.
Our job is to love everyone.  If we do that, everything else will fall into place.