I wouldn't want to use it in a steady rain. I've used mine in sprinkles with no problems -- just wipe off the drops between shots before they have a chance to find their way inside.
An old trick that still works well: If rainy weather threatens, put a big zip-lock plastic bag in your pocket. If it starts to rain, slip the bag over your camera (strap and all) leaving the open end down -- this keeps water off but prevents humidity from building up inside the bag.
When you want to take a shot, bring the bagged camera to your eye, fold back the bag, adjust as necessary, and shoot. A broad-brimmed hat will help keep the rain off while you're making your final adjustments.
In heavy rains, you can cut a hole in the bag and poke the end of the lens through it -- secure the bag to the lens with a lens hood and a UV filter (which also will protect the glass during wipings.) Reach up through the open bottom of the bag to operate the controls. The bag will obscure your view through the finder, but you'll still be able to take pictures, and your camera will be pretty well-protected.
