WARNING SPOILERS
I prefer vol.2 to vol.1 but i think most people like the action driven vol.1 more whereas this is the one that fleshes out the story. V1 has the amazingly overblown fight scene with the Crazy 88's (think that's right) and the showdown with Lucy Liu's character and in V2 the fighting is more emotional where the Bride has to look within in order to escape being buried alive and then the ultimate showdown with Bill himself which has hardly any fighting at all. I think the ending is perfect the way it is. After the over the top fighting sequences that came before, the final 'fight' is the opposite and while allowing the audience a chance to breathe, highlights the relationship that came before with Bill and shows how emotional it is for the Bride to finally face him again along with the shocking reunion with her child. It wouldn't be suitable for her to brutally chop to pieces Bill who is the father of her child while the child is sleeping in the next room, so he's given the easy way out. Bill throughout the two films almost seems to want the Bride to get her revenge after all she's been through but he won't give it to her easily- she has to earn it.
Bill's brother, Bud, is a favorite character of mine and he finally gets some proper screentime, and his fractured relationship with Bill adds another layer of depth to Bill's personal and business relations.
This is the one film of QT's that screams for a sequel and one is set up perfectly. I don't think I'd change a thing about this film.