You get a lot in this season. Ezra's power in the force grows, but his tendencies towards accepting the dark side cause him and the Ghost crew some issues that are essential for character development. Sabine's back story finally gets flushed out and she begins to confront her own destiny. But to be honest, the best part of this season is THRAWN. I wish he would've been a bit more imposing in voice, but his presence and action in all the episodes does proud the creation from Timothy Zahn's books. As ruthless as Vader, but calculating and utterly patient, he shows very well in the series why he became grand admiral. He sees victory in increments as he is aware the campaign to crush the rebellion is a slow one. I also like how a lot of Ralph McQuarrie's designs are used throughout the show, like the precursors to droids and combat vehicles that will someday be seen in the original trilogy, paying homage to one of the visionaries that helped breathe life into this sci-fi giant.
You get a LOT of explanation about how the rebellion grew, organized, and acquired personnel and materiel for their war effort. Several times in this season you see the characters risking all for gains unseen, and the culmination to a large battle scene did not disappoint. You also see a few more faces in the Empire and the development of the TIE Defender, the induction of some of the rebellion's most crucial members, and that's all I'll say for now.