Material Opacity in viewport? I'd like to do motion graphics type work in blender and it would be really helpful if I could see the results of keyframing material opacity to cut items in and out of view.

Blender internal is sufficient, using shadeless materials.  I could have swore there used to be something in view options.  Any ideas?
Object panel > Display > Transparency Checkbox.

This works for Blender Internal but not Cycles.