Nikon's weather sealing is pretty good compare to other brands..
Report from an Antarctica trip:
"The top LCD on a 5D MKII spontaneously cracked; Another 5D MKII had a jambed on lens caused by a loose screw, a 1Ds MKIII reported intermittent problems; a 1D MKIII kept reporting Error 99; one Hasselblad reported electronic lens connection problems; two Canon G9's failed (no G10s had any reported problems), and a Nikon 80-400mm lens came apart. No Nikon bodies (mostly D700s) failed in any way.
The largest group of failures through were among the Canon 5D MKIIs. Of the 26 samples of this camera onboard, one quarter (six) failed at one time or another, and while three recovered, the other three never did. In all cases it appeared to be water or humidity damage. Of particular concern were two cameras which stopped working while completely protected within Kata rain covers during a light rain ashore..."
http://www.luminous-landscape.com/essays...rked.shtml
Another website:
"The camera held in my right hand is the D700. Our storm chase vehicle, the camera, and yours truly were covered in dirt and dust by day's end -- but safe and uninjured. It literally took two days to clean everything. Although VERY dirty, the D700 performed flawlessly and never stopped working!
As weeks passed, and the record-setting severe weather season continued, the D700 was subjected to heavy rainfall and, believe me, the camera got SOAKED. It was constantly around lightning and, at one point, was hit by a falling hailstone. Still, not so much as a hiccup. It performed reliably on every level.
While hurrying toward the end of a mission, the D700 was even dropped onto a concrete driveway. The circular polarizer was destroyed, but the camera was fine, and continued to perform as if nothing ever happened.
So, with respect to durability and weather-resistance, I give the D700 an "EXCELLENT" rating."
http://www.jimreedphoto.com/content.html?page=5