I used my K20D and 50-135mm F2.8 lens in the rain recently at Disney World, and even used them all the way through Splash Mountain, including the big drop. This is essentially a log flume ride, for those not familiar with it, and you get pretty soaked at the end. I left it out and shooting all the way down, and this was the only time that water came in hard enough to actually get droplets on the front element of the lens, past the deep lens hood.
There were no problems whatsoever with the camera or lens. I only wish that I had the 16-50mm F2.8 lens... that's next on my list.
I have over 650 pics from the trip in my
gallery so far with more on the way, if anyone's curious for more K20D photos... I took 4,035 in a week.