This past spring I posted about a subtle processing difference that led my father, an astrophotographer, to choose a Canon digital SLR over a Nikon, even though he could have used my Nikon lenses for day-to-day photography and saved a lot of money.
According to DPReview's spec list, Nikon's new D80 DSLR, the successor to the D70s that he was considering, now offers the option to turn off (as well as adjust the aggressiveness of) the "high ISO noise reduction," which was the problem that pushed him to the Canon side. The new Nikon also features mirror lock-up, which was my dad's other deal-breaker.
But he has the Canon now. I still have the lenses, and no camera to use them with yet, but when I get my own DSLR someday, it will likely be a Nikon, since I'm not particularly concerned with those two features anyway.