problem comes when a message "runway slippery when wet" is indicated that slippery inferes a MU reading of .05 ( someone correct me if I'm wrong!) therefore if the runway is wet do you plan using slippery runway data? no of course not because it is very likely that the braking action is considerably better than that, so a careful wording should be used because for some guy's this kind of message would stop inbound operations. Doesn't take qway from the fact that more info should be posted on the ATIS though.