Nikon swapped the bracket control on the D200 for the review button on the D300. To select bracketing on the D300 you use the one of the programmable buttons (default is Fn, and the DOF preview and AE-L/AF-L are assignable, as well). Frequent bracketers might miss the dedicated control, though.
On the upside, the D300 sports a big, bright 3-inch LCD. Increasing the display size hasn't adversely affected the ergonomics of the camera at all.