I think it's a feel thing. When I went from a D80 to a D200, the D200 took a good bit more effort to fire the shutter, and it's because of the extra gasket sealing related to the shutter release. The D300 feels identical to the D200.
At first I'd preferred the D80's lighter action! Then the D200 became more familiar... and I acclimatized.
The D7000, to me, feels more in the D80 style. I'm actually preferring it because I feel it enables me to more consistently squeeze the shutter release more than jab. It reminds me of my older Olympus OM-1 which had one of the smoothest shutters ever made.
It's a subtle "feel" thing (IMO), but one that can easily be adjusted to.