I have often substituted all purpose flour in recipes calling for bread flour, because I didn't have any on hand. I had never even tried baking with it until yesterday. OH. MY. GOODNESS. What a difference. Really! I didn't think it would make that big of a difference, but it did. Yesterday, I made sour dough bread with it; I liked the bread fine before, but now, it's FANTASTIC! Why has no one ever told me this before???? My recipe called for all purpose flour, but I thought I would see what bread flour would do, because a lot of sour dough bread recipes are made with bread flour. It was so yummy! The only downside was it was so good, and I didn't want to stop eating it... (I'm trying to get OUT of maternity clothes!)
You can learn about the difference between the two flours, HERE, and HERE.