I've floorstanders for all my speaker (except the center of course)....the rears especially really benefit from this....Mid to Low bass (which have some directional sound) improve alot...example is scenes like IronMan2 where Hammer drones drop everywhere from the sky for the showdown at the oracle park is marvelous. Instead of hearing / feeling the bass from the Subwoofer, now the rears also can have bass...giving the sofa a nice thump. Other movies like when a dragon flaps its wings from the rear to the Left rear and then Right rear is also felt.

For me, the days of the rears doing its job as ambiance speaker is nearly over with the intro of HD audio...even for normal DTS/DD producers and Sound engineers are putting lotsa info for the rears.