I was offered a sponsorship to modify my car to the G-Power kit. In fact, I'm still in conversation about it. I could save 3K on the kit, but the company wants to charge me 15K for repaint/labor. I-don't-think-so!
But seriuosly, after I read the installation manual, all I can say is "TRULY PERMANENT" and "DESTRUCTIVE INSTALLATION". I like the fact that the parts will attach firmly (due to all the adhesive required, and the screwing, and the cutting, etc), but I do not like the cutting of the wheel housing (front and rear), or the flanging of the rear arches, or the soldering of the wiring, or the cutting of the crossbar, or the cutting of the support bar in the fenders, or...
So, if you don't care about the, AHEM!, "destructive installation", go ahead and slap on the kit. You'll probably beat me to it ... cause I think I'll go with Lumma CLR 530.
... still deciding.