Yeah, the 5D2 is very dependable, but I prefer not to push my luck.
About a year ago I was shooting some shots in a mountain town but was caught by a sudden torrential rain. Despite the fact I didn't bring a rain coat for my camera, I kept shooting in the rain - trusting the camera to hold its grounds.
Even though nothing major went wrong, there was a problem with the joystick on the back side; there's no response when you push the joystick to the left, and the problem seems to be from the water-drenched gaps between the camera and joystick pad. Fortunately, sticking the camera back in the dehumidifier storage for a day.
Again, even though the body is dependable, I rather not push my luck and would stick an extra camera raincoat in my gear pack if possible.