Star Wars: The Last Jedi Trailer Reactions - 8 Ups & 2 Downs
2. Luke's Ambiguity (And Mark Hamill's Acting)

Given that he's the titular Last Jedi, it was always inevitable that Luke's story was going to be pretty central in the sequel, and this trailer definitely sets out its stall to explore some of the major beats in that arc.
After his "the Jedi must end" bombshell at the end of the last trailer, Luke's in full ambiguity mode here, at times terrified by Rey's powers and at others clearly seduced enough to teach her some things. And though it looks like she will ultimately win him over (possibly thanks to an external tragedy involving Leia as added drive), there is still some uncertainty around his true nature.
The trailer seems to imply that he is neither good nor evil - that he's more a centrist, chaotic element seeking to pull everything down to stop the sins of the past from repeating - and it's a very intriguing idea.
Add to that the fact that Mark Hamill legitimately looks like a good actor (even speaking charitably, he wasn't in the original series) and the excitement to see more of Luke is huge.