I've just stumbled on the interesting ( and certainly one for your bookmarks if Canon is what you use) website Canon Field Reviews (CFR) authored by Pro Nature Photographer Ole Jørgen Liodden of Norway who tests Canon gear under extreme real life conditions.
Liodden took his Canon 7D on a three and a half week week photo expedition to Antarctica, and put it through extreme and hard use under prevailing bad weather conditions, and reported that it performed flawlessly. He chose to use the camera with a battery grip for better handling, and it (the grip) seemed tighter and better sealed than the one that fits the Canon 5D Mark II. He reports that his 7D had absolutely no problems with snow, rain and water (sea spray). He also used a Canon 1Ds Mark III with no issues at all (as expected from such a camera).
His conclusion:
"The 7D performed as I had hoped, surpassing 10,000 exposures without a problem. I must admit that the 5D Mark II surprised me as well with its build quality. The 1DS Mark III camera is the most rugged and best weather sealed, but the 7D and 5D Mark II (without battery grip) performed 100% in my opinion."
Hmmmm.