I honestly think he was the best cinematographer to work in film. Even if it was just for his work with Bergman (who is my personal favorite), but also look at how amazing Tarkovsky's Offret is, in addition to Another Woman, Crimes and Misdemeanors, The Unbearable Lightness of Being, and many more.
I think I'll be putting in some of his films over the next few days to honor and remember his art.
Edit: Dug up one of my favorite quotes from Bergie about Mr. Nykvist: "we are both utterly captivated by the problems of light, the gentle, dangerous, dreamlike, living, dead, clear, misty, hot, violent, bare, sudden, dark, springlike, falling, straight, slanting, sensual, subdued, limited, poisonous, calming, pale light. Light."
Ingmar Bergman is probably one of my top 3 director's - and the work that him and Nykvist compiled together is simply fantastic. IMHO he is responsible for capturing some of the most memorable, and ground breaking images in all of film.
He will be missed, but the man has definitely left a legacy that will live on for a very, very long time.