I do it but only when the road is very lightly wet. In the UK we get a lot of very light rain that can cause the road to become very slick as the oils in the road come to the surface but don't get washed away by the rain. It's at those times that I will 'check the road' but then only below, say, 5 mph when I'm getting ready to stop. Usually, I'll leave my foot down as I stop. If it's been raining hard or for a long time (hours or days) then I usually don't bother as the oils have had a chance to wash away.
I hope that helps.
So if it's only rained a little bit, you check the conditions; and if it's rained a lot, you don't bother?
I guess it is a good indicator since you put your foot down at such a low speed, but I figure if these two sides are so cut and dry, then the braking option should be easily decided upon.
In this situation, I would think you would just need to brake more cautiously during a light or early sprinkle. Then a bit more thoroughly in more dry conditions.