Oh, what an engaging, well written story this was! I don't think I've ever read a 30,000 words this fast! I mean, I couldn't stop reading, once I finished each part I had to go straight to the next to see what would happen. :D
Your teenage Snape was great! And I loved Harry's POV, and that was a brilliant way to do time travel. I loved how Harry gradually became audible then visible then solid. I loved the Dumbledore scenes as well, especially the one with Harry. And another favourite scene was when James went to Snape and asked who the hell was that Harry Potter. Hee! I have a thing for moments of revelation like that - and I had totally forgotten about the Marauder's Map, too! What else, what else? Oh, I enjoyed Hermione and Ron a lot. And Neville - which is not usual. :)
I liked that Harry decided to stay in the past, and thinking of this as an AU parallel to the canon one will help my brain hurt a little less about all the possible ways this future could unfold and possible paradoxes. :P But it's so intriguing!