Body & Design
With the exception of a couple of button tweaks and a revised card door, the outside of the D300S is almost indistinguishable from its predecessor. The tiny speaker at the bottom right of the rear panel and three microphone holes below the model number are the only significant physical changes.
In your hand
Most high-end DSLRs feature Magnesium alloy construction but the D300 stood out as a particularly weighty and well-constructed example. And, although the D300S carries-over this impressive build quality, it no longer quite stands out from its rivals to the extent its forebear did. The D300S is still a stand-out camera in terms of ergonomics, however.
Although the fine detail of ergonomics can come down to personal preference and hand shape/size, the basics are universal - a well-placed button may be slightly more or less comfortable for different people, but if it's readily accessible to everyone without the need to reposition their grip, then it's still well-positioned. And the key features on the D300S are well positioned - control dials and most adjustment buttons are within easy reach and the two custom buttons on the camera's front are also readily accessible. It's only really the White Balance, ISO and Quality buttons on the top left of the camera that raise any real doubts (I find them accessible enough but not everyone in the office likes their positioning, when holding the camera up to the eye).
Side by side
The only other APS-C camera on the market with an autofocus system as sophisticated as the D300S is arguably Canon's EOS 7D. Although the competing models from Olympus, Pentax and Sony come close to matching the Canon's 19 cross-type AF points (if not quite the Nikon's 51 points, of which 15 are cross-type), none comes close to offering its level of sophistication of AF-point selection. And, while the Nikon offers fewer methods to ensure the correct focus point is being used, it is capable of tracking objects across different focus points by both distance and color which again is unmatched by the competition.
You can see the dimensionally identical D300 next to some of the D300S's other peers by clicking here.