Suppose Draco Malfoy introduced himself before he started acting like an ass. What if he had asked Harry's name before insulting Hagrid? A friendly handshake in Madam Malkin's leads to an alternate but realistic universe which is eerily like the canon.
I really liked this retelling of Harry's first year had he been sorted into Slytherin after becoming friends with Draco at Madam Malkin's. While it's possible some machinations were in effect to gain Harry's friendship and trust, I think by the end of this book, Draco and the Malfoys and the rest of the Slytherins are truly on Harry's side (even should the going get tough and they need to choose a side in the coming war - if that's still going to be a plot device). When it comes to fanfiction rewrites, the plots nearly always stay the same book to book - Stone, Basilisk, Sirius, Tournament, DoM, Astronomy Tower, Horcrux Hunt. While the group may be different, they still figure everything out at certain times in order to have the pacing land relatively in the same place as the original books - certain characters wind up in the same situations, and things are dealt with at the last minute, often in the same way.
I do wonder if book 2 will focus more on Harry's Parseltongue ability and the Chamber - if the diary makes a entrance - Ginny's sorting so that she can still get the diary back after Valentine's Day. Oh God, Lockhart is going to be infuriatingly difficult to muddle through again. At least this time, I'll just try to keep the wholesome goodness that is Branagh in my mind. Now I remember why no one likes the CoS book *shudders*