I think I can answer comment number 2.
The 800JB is a 2 platter drive therefore the mechanism should be much more simplier to the 1200JB which will lead to less noise and less heat produced.
However, what cannot be explained is the increase of access time. I believe, given exactly the same drive, but one with 3 platter, one with 2, the 2 platter drive should have a lower access time due to the 'lighter' heads. WD must have somehow slowed down the drives access time so that it cannot perform faster than the 1200JB.
Whats irriatating is that it is even slower than the 1000BB-SE/JB. Which has a 33GB platter, and significantly lower transfer rate.
And I have just purchased a 800JB today, thinking it would mimic a 1200JB's performance...