This movie gave me a new perspective on Vol.1, and now that I can consider both Volumes as one whole movie, I have no difficulty in giving it a 5 star rating. Tarantino once again shows his incredible talent at keeping long and slow conversations both fascinating, tense, and unpredictable. The cinematography is once again brilliant, although not quite as mind-boggling as Vol.1. However, I think this was done on purpose.
You see, the reason why this shed new light on Vol.1 in my mind is that I think the first movie was meant to show The Bride's early euphoria and motivation to get revenge; bright and vivid cinematography, bloody action scenes and downplayed conversations in that movie were done to achieve this. No thinking, just running ahead swords-a-slashing.
When you get to the second movie, however, everything starts getting more grounded in reality as story elements are unveiled and the revenge plot gets closer to its conclusion. The brownish and greyish colours throughout the movie and the long conversations show this. It's the early euphoria breaking off.
So when you see both as parts of one whole movie, the lack of substance in the first is no longer a problem, and the lack of action in the second isn't as well. What is left is one of the best-made and most fun movies from the last decade, and a definite classic.
In a sentence:
Completes the first movie so perfectly that they both combine to make one of the best and most enjoyable movies of the last decade.