I've got a 5D3 with a Meike grip on it. Mine's the one with the joystick on the back of the grip whereas most grips don't have it. Mine cost around £45 off Amazon and it's worked flawlessly since I've had it. I used to use 3rd party batteries in it to start with but had problems with some of the batteries after updating the 5D3's firmware so I bought a bunch of Canon batteries instead. I did have a Pixel grip on it to start with, it was the first 3rd party grip to be released, but it suffered from a battery drain problem so got the Meike instead. I've also had Meike grips on a 550D, 650D, 60D, 2x 7D's, 5D2 and now the 5D3. I've not had any problems with any of the grips on any of the bodies, they are very well made, fit the body very well and the buttons need similar pressure to activate as the body buttons.
I've now got a 70D and it's got a genuine Canon grip on it, bought for £159 (over 3 times the amount of the Meike grips), and it doesn't feel any different to the Meike grips that I've used. I would of happily used a Meike grip for the 70D but the wife bought the Canon for my birthday just after I got the camera. I would quite happily use Meike grips all the time and I would happily recommend them to anyone wanting a grip. I cannot in any way, shape or form see why the Canon should be 3 times the price as it's definitely not 3 times the quality of the Meike.
