I'm a relatively recent, but very enthusiastic, convert to sushi. (In my chowhound-cred defense, I grew up in North Carolina and spent much of my 20s in England, two places where there is great food but not much sushi.)
Anyway, now enlightened and living in Boston, I can't get enough of the stuff, whether a casual pack of California rolls from the deli at Whole Foods or proper assemblages at Japanese restaurants. I am warming up to the big time, dreaming of a trip to one of the really great, expensive places that was listed in today's (3/28) New York Times travel-section article on raw fish in Boston: Oiishi, or the sashimi bar at Clio.
What I want to know is, what makes great sushi? How should I educate my palate so as to be worthy of higher experiences? I grasp that freshness is important, but what does ultra-fresh fish taste like? Look like? How does creativity come into play in sushi preparation?