i really liked the but there are still too many things left unkniwn and now that the flashbacks are over, probably wont be explained anymore..
1. what happend to the spiral one?
2. how did obito know where exactly naruto was born?
3. how did he get the knowledge to break the sealing on kushina?
4. why the name "tobi" and since when??
Anyway, concerning nagato, he probably joined when yahiko died where he raged and summoned GM, after seeing what he is capable of, he may thought tobi was right and turned his back on yahikos idea.. would also explain why he didnt resurrected him. Yahiko wouldnt have been on their side anyways.
Still want to learn more about Nagatos past.. i want to see everything
Btw, yahiko is awesome, great leader. kind of ironic that yahiko also represented the pain grp and was used as the leader of amegakure after he defeated hanzou.
btw, why killing hanzou in the first place? just to spread fear and get respected by the people?