I am in the non battery camp, I had them for my film (then it was handy for that auto advance, and the cool sound of the motor advance (bet lots remember that sound), but, with digital the need for auto advance is gone.
My grips have rarely been used, and collect dust, I prefer the smaller cameras, and find the extra bulk of the battery holder not and advantage.
It does give the veritical control shift, but I am so used to keeping my hands on the controls, that It is totally automatic whether I shoot horizantal or vertical, adding a battery grip, would just make me have to retrain.
if you do buy one, first go for the el-cheapo aftermarket ones,, see if you like them, before considerng buyng the way more expensive Nikon models (and yes, the Nikon models are higher quality (can tell in the control dials).