In Truce at Bakura, within days of his death, his spirit in old man form appears to Leia to ask for her forgiveness. She freaks out, and says she can never forgive him. Never, never, never. Maybe for torturing her, but never for doing it to Han, and turning back at the last minute is all very well and good but it doesn't make up for everything he did before that. And she will never call him father. Her father was Bail Organa of Alderaan, and he was a good man. Don't come back, she doesn't want to see him.
Then Han comes in and asks her why she looks so upset, and Leia is angry and scared and tells him she just saw Darth Vader's spirit, and he tenses up too. At the end of the book Leia reluctantly says to a presence that doesn't speak that she doesn't want to hear from him, but if he wants to be proud of her and what she's doing... well, stand back and watch. Leia is kind of awesome.
In the rest of the EU, Vader is always on every list of evil people, along with Palptatine. Many years down the road someone asks if a serious pilot wasn't able to bring a joking one up to the mental age of, say, ten, and is told that Darth Vader and the Dark Side of the Force couldn't do that. Only Luke ever says he was able to make up for it, and Luke, well, he's the idealist, and even he sometimes lumps his father with whatever the worst villains ever are for the book.
General consensus is "Well, Luke, it's actually a good thing that he died then and there, since we'd have had to execute him if he hadn't."