A very good story in general and a exceedingly good Peggy Sue. Serious in nature, yet filled with humorous moments. Sasuke never becomes a Marty Stu despite foreknowledge and advanced training, largely because he is focused on building Naruto up as opposed to fixing everything himself.
Sasuke is very well written. He is emotionally shattered and he knows it. And yet he holds on to the hope that Naruto, the friend who never gave up on him, will one day be able to fix him. And through dozens of small changes, encouragements, and interventions, he works to build Naruto into one of the most powerful ninjas ever.
Also, has one of the best justifications for Kakashi constantly being late that I have ever read.
Unfortunately, since the story hasn't been updated since January 2010, its probably dead.