Well I was out at thunder hill last weekend...will be out at laguna seca on the 6th with newly installed nismo bracing and these. Nismo bracing is mainly focused on the rear, gtspec all about the front so I'll let you know if my butt can tell the difference. In my experience bracing is one of the cheapest, highest value things you can do for for car... I've played with bracing on a crx, pontiac grand prix, escort, 996 911, 84 carrera targa, and even a 86 toyota pickup, and though most of those have noodle frames they all responded extremely well to bracing. On the porsches it seriously sharpened the turn in steering response and firmed up the rear giving significant confidence and making the car more tossable.
The only thing cheaper but worth more is foaming the frame rails and pillars.
The only word of caution I'd have is that bracing like gtspec probably seriously eliminates some crash safety of the car...with that type of bracing tying things together in a front back fashion across frame and sub frames almost certainly means your crumple zones will not work as intended. The nismo bracing should be safe enough as the ties are pretty localized and mainly side to side. But I'm sure they're nowhere near as effective as the gtspec models.
To sumup the commercial, yes, bracing very good
