I just got done with $2100 worth of suspension stuff (roush kit, LCA's). I think the upper control arm is a race only thing.
I doubt if you would need it on the street.
If your lowered and have a street strip car or a track car you may want to look into it for launch adjustment, but you'd probably be better ahead with other suspension mods before you got to this step, if you are racing.
For a street car in my opinion the upper control arm falls under the "not needed" catagory.
Jack