Quite possibly the best sequel ever
I'm shocked at seeing rating this low here. It was the reason I was putting off watching it for a while thinking it's a throwaway cash-grab sequel, but now that I've seen it I can easily say that it's about as good as original was. Which is pretty damn tough thing to do considering how good the original is.
More American Graffiti brings back most of the characters from American Graffiti and shows them being grown ups, facing adult problems and ultimately moving away from their high schools friendships. It's darker in themes and tone, but nostalgia is the main drive of the movie. It's faithful to the original in how it keeps intercutting between stories and uses period music extensively. It's uses the variable framing technique that used in recent Grand Budapest Hotel (every story in MAG use it's own framing).
Perhaps it pales in comparison to original in some ways (I've seen it some time ago and can't really compare), but it's a great film on its own.