I do like that another non-dark side Skywalker was revealed to exist. It allowed for Vader’s “If you will not turn, perhaps she will,” moment and Luke’s reaction to it.
Interestingly, if you look very closely at Vader he is holding Luke’s lightsaber at that point. He was supposed to have thrown it away. oOssibly why it is a bit off how Luke comes out of nowhere as there is footage not in there.
Also, this is the first example of “Force interrogation” we see, pre-Kylo Ren…
That is one of if not the hi-light of the OT for me. The music for that sequence is just superb.