"Real World" test I just took 32 Large Fine JPEGS of the best quality with my D7000 before it slowed down. Then it took the Sandisk 45MBs card very few (about 2-3) seconds to clear the buffer.
I expect that if it was profitable on the D3, we can expect a buffer upgrade option for the D7000 or/also they may soon come out with a D7000s? And, if $500 like the D3, I probably won't get a buffer upgrade. It did not make a huge difference on my D3. And, I have not had a buffer overrun since buying my D7000.