I use my two D7000s in all sorts of weather, lots of torrential rain, dust, sub-zero temps, general horribleness...
Combined with a good set of lenses (mainly 11-16mm, 17-55mm, 70-200mm but also 35mm DX, 60mm AF-D and several other lenses in the past) I've yet to have issues with the cameras. Coming from a pair of D2x bodies my expectations were low in terms of how they'd fare in bad weather but I have to say I'm impressed. One of my main concerns was about having the audio input flap open while filming with a mic plugged in.... effectively, the rubber flap is one of the environmental seals but again, I've not had an issue.
This was shot on a D7000 and was basically two full days of non-stop rain. Roads to the venue were flooded halfway up your car door and even our team Gore-Tex suits got to the point where they just couldn't take any more. A thoroughly miserable two days:
[YOUTUBE]gWXs0jRuYk[/YOUTUBE]
Can't seem to get the video to embed so here's the link:
http://www.youtube.com/watch?v=-gWXs0jRuYk&feature=share&list=UU0TvnAKz0Dh17O8htO7a4VA
There is definitely a piece-of-mind to be had from extensive weathersealing and those cameras that play on it (D3/D4 etc) but it's amazing what you can put consumer-grade cameras through; we've used Canon xxD bodies for years at work and most have fared well in the hands of journalists who really don't care about them, as they're the company's property and not their own (my kit is my own). We've recently had a glut of 30D and 40D bodies going down with an intermittent shutter button issue, but I put that down to overuse than any weather-based issues. You also can't account for a journo who, when the pop-up flash kept popping up when they didn't want it to, glued the flash in place
Personally, I still trust my Nikons more than the Canons I've used but nonetheless, how much abuse 'regular' cameras can take is often underestimated