As far as I know all sites reveal the hands at showdown.What do you think about rooms revealing them anyway? Maybe you did not realize it but 888 reveals all (non folded) hands in the replay. I believe this is happening at Poker Stars too.
Try it and see - next time you wonder what they had check the replay.
Anyway, if not too many people are aware it is an advantage.... maybe I shouldn't be letting the cat out of the bag.