I shot my K200d with DA 18-55 kit lens and AF220T flash for about 5 hours in the rain during field work (heck, amphibians and rain are kinda connected...) without any issues whatsoever, and also got caught in heavy downpour recently, through which I had to go for about 10 minutes. Nowhere to get out of the rain, so I just relied on the 200's sealing... Also no bag, or rain cover, or plastic bag for that matter in both cases...
The non WR DA 50-200 braved the downpour beautifully, but dripped quite a lot of water out of the barrel, but it's still clear and without issues. Also, I once practically buried the whole thing into very fine wet sand thanks to a fall in a gravel pit. Pentax survived this with flying colour, although the barrel grinded a bit afterwards
Well, at least that rain afterwards got all the sand anyway out