I have one for the warm side and one for the cool side. Temps on my range from 90-93 and 80-84 respectivly (controlled with clamp lamp dimmers). It does suck the humidity out so I use bed a beast as a substraite and mist a few times daily.

Since I have lamps, I don't use any UTHs. I figure if you can get temps with one you don't need the other. If you can get temps correct with the lights then you don't need the UTH or vis versa, but that's just me.