The only thing to add about riding in the rain, is that it sure is nice to be retired and squeeze in winter rides between the major showers. Fenders and flaps make wet days quite bearable.

I concur that in a downpour at speed you just get mostly wet, trying to keep 'core dry' and 'extremities warm' is doable. For me it needs to be above 45f (and not a downpour) if I want to enjoy the ride.