Don't worry, the eBay Chinese $60 knockoffs should be showing up shortly. With any luck it will beat the genuine grip to market. I don't mind the eBay grips.
Going back a few years the genuine grip for a 40D died and was replaced with an eBay knockoff, it still works perfectly for my daughter. I destroyed the tripod thread in a 5D classic grip years ago and it would have cost $160 to have repaired so I tried an eBay knockoff which was indistinguishable from the genuine except for branding. It banged around in my bag for years and probably did over 200k shutter actuations before being passed on to a friend who uses it on a daily basis.
So in my limited experience, the knockoffs build quality, switchgear, buttons etc are perfectly fine. I'm just going to buy whichever comes out first.
BTW don't overtighten anything you put into the tripod thread on your grip. It's not as solidly anchored as the one in the body. SpiderPro plates, Black Rapid straps etc which use the tripod thread can easily be overtightened, tearing the metal thread away from what ever material the grip base is manufactured from.