Why does nobody think about GS the follwoing way?!:
Gearscore represents the gear you have. So (if you did not buy your char, and most of the people in WoW did not!) you farmed it, so you know how to kill the bosses and so GS CAN represent you skill too.
And lets say there would not be a gearscoreaddon: If your account has shitty gear they wont get you for the group, or are ther NO GEARCHECKS at your servers?!
And if you want to build a (rnd-) group, there are only 2 possibilitys: You either know the ppl and how they play, or you look at the gear they have.
I think gearscore only speed up the gearchecking process.