As far as I know, all the raiding guilds on my realm use this. It comes very handy at times, for example in some extended fights like VR I get to a point where as a Shadowpriest I need to chug down mana pots whenever the CD is up. Since I still get hit by the occasional aoe, and stopping to bandage is too much dps time wasted, having more than one HS is very handy.