Now when transmogs is available (Thanks Blizz, I love it!) there also are many nice looking combinations to use out there. Because of this I think you (Blizzard) should consider allowing hide options for more gear than just cloak and helmet.

My own thoughts are:

Gloves.
There are several nice looking bracers out there, but because of gloves you almost never see them.

Belt.
Many leggings and robes already have visual built-in belts and it's visual appearance sometimes gets destroyed if an extra belt is shown on top of this.

Shoulders.
There are some outfits which actually would look better without them.

Tabards.
Hiding of tabards would allow you to farm reputation but still allow you to enjoy the visual appearance of your transmoged armor.

Also instead of having these options under Interface-Display, why not put small buttons on the character tab at each slot allowing to easy toggle between show/hide.

And finally, many robes have gaps in them which doesn't look so nice when leggings are shown through. Why not make it so that every time a full length robe is equipped, the leggings are automatically hidden.