I don't have much more to say at this point, though, probably because there are only a few episodes left in the series, and therefore not very many spoilers if you've watched up to this point. There was just one little thing on episode 11:
Chapter 11: The Day of Black Sun, part 2: The Eclipse
Sokka tells Aang, "Whatever you decide, I’m with you." This is almost the same thing he says when the issue of accepting Zuko comes up. He's developed a strong sense of loyalty to Aang, but I think his humility in twice deferring to Aang's decision is also a sign of his maturity.