It's pretty obvious that Walt is dead by the end. This speculation that he wasn't is kind of silly. Thematically, emotionally, and storytelling-wise for Walt to still be alive just kills the momentum of the entire episode.
As for Jesse, there was a great BuzzFeed article (ugh, I can't believe I just said that) about how for most of the series, anytime he'd be in a car with someone (Walt, Mike, Hank) he was never in control, never free... the point of his last scene isn't that he's going to have some easy carefree life, the point is that at last he *is* free. And that's why we got that crazy happy laugh from him. Vince Gilligan noted that Jesse's life wasn't going to instantly be cupcakes and roses, but pointed out two things:
1) Jesse's arc had the opposite trajectory of Walt's, and that the writers all felt that he had earned a modicum of a happy ending after everything he'd been through.
2) Gilligan himself likes to believe Jesse "got away" and was able to start over, but obviously intends for each of us to come to our own conclusions about it.