I've heard they tighten up the front end feel but I'm not sure about actual results. Ebay has some nice packages with replica H-braces and strut tower braces that I might pick up someday.
Picked up an ebay front strut bar ($18) not too shabby if you are patient and dont compete with craziness http://mingtai.us/ixiz/9-2x/mod-frt_struttower.htm
the h brace is good for when you remove the unibrace. non us model sti and wrx dont even have a unibrace. you can save some weight by removing it and the h brace is a better support in design. its H shaped, solid ,and it goes right under the motor. where the unibrace is u shaped, tubular steel, and connects under your bumper.
is there any difference between the ebay ones and the cusco model besides price? as far as I can tell there both light weight aluminum.