In six years I've had three customers I can remember that had water damage. Two had dropped their systems into water (fully submerged) – total losses. The third was shooting at the base of a waterfall and had a ballpark $600 repair bill for his body (though it did take 2 repairs to resolve the issue, which is unusual - the 2nd repair was of course free since they didn't fully correct the issues in the first repair).
Whether the lack of any other repairs/service/damage is because the systems are quite solid in adverse conditions (though definitely not "fully weather sealed") or because users tend not to push beyond light rain situations and use reasonable precautions like a plastic trash bag* when things start to get dicey, or because customers who shoot in monsoons more often opt for a fully sealed system I cannot be sure. But in practice I've found it is a topic that comes up much more on the forums than among our customers.
Personally when I'm shooting weddings I continue to shoot without concern in light rain and sprinkles but have never pushed beyond that with any of my gear (Canons, Fuji, or Phase).
*a trick I picked up first from Guy Mancuso - the magic being not in the sophistication of the approach but in the dirt cheap and ultra light/small pack weight/size