The battery grip for my Sony A7s has just arrived. It really fits well the camera, gives me a much better grip and the buttons on it are very helpful. Of course the greatest advantage for me is having 2 batteries, the A7s is a very power hungry camera !. The whole combo is smaller than I imagined and it makes the camera more sturdy for handheld work. It is also easier for me to shoot video on my monopod or tripod, since the screen is easier to flip (without the grip, the bottom of the LCD screen is almost sitting on the baseplate). The lens is also much higher from the baseplate which makes it easier of me to change apertures and focus better.
You can check the grip here: Sony VGC1EM Vertical Camera Grip Accessory (Amazon.co.uk)