Gabriel's death scene was sad. Looking back at his first appearance, I never could have imagined that I would have really felt for him in his final moments like that. His, erm, media appearance at the end was great, though
As for Chuck being God, I honestly have no clue. I'm leaning towards it being true, though. Either way, it definitely opens up a lot of great stuff to think about. The ambiguity of his last appearance was one of the coolest parts in the entire show.
Funny enough, Gabriel and Chuck have definitely shot up the list to become two of my favorite recurring characters (that aren't Bobby and Castiel), alongside Ellen, Jo, and Ash.