I am a bit skeptical when it comes to visions, but Stephen's vision of the real Stephen is obviously not being sold as something that indeed occurred. Not to say that visions cannot occur anymore, which would be far from the biblical truth. But we all know how much abuse had been done.
This being said, we see a great idea behind the movie, to have the boy go in his dream through a quick time travel throughout Christian history. A low-budget movie, but well-made and without any expectation for more. It fulfilled its purpose in a wonderful way, to educate both children and adults about our history, and not to repeat (or at least to a lesser degree) the endless accounts of Christians going on a holiday trip to Rome and coming back with a big smile, knowing little about what place they had been.
This movie did probably a more important job than many other lengthy movies and dozens of books written without discernment and watering down the boundaries of the church.
It is very important in our times of increasing ecumenism, when we are about to forget the past of the 'church' and think that everything is at peace, just right before the other side will show one day its ugly face again.