I haven't bought a grip yet, but I intend to. I'm not SO concerned about the tripod mount falling apart, but I am concerned about it being rock-solid. After all, the reason the camera is on a tripod is for a solid platform. Rocking between the camera and the grip, or a grip bottom that is not flat (leading to rocking between the grip and the tripod) would make the function of the tripod mount itself moot.
I suppose you could ask if there's wiggle between a 3rd party grip and a body. I haven't heard of any reports about that. I suppose that becomes a larger concern if you are shooting on a tripod with the camera mounted sideways or upside down.
To the OP, I have thought about adding a grip to my 60D as well. But for the life of me, I don't see the big advantage it would give me other than maybe looking cool.
A battery grip is less about the battery part of it and more about the grip. If you compare a gripped body and a non gripped body each mounted with a 70-200, you will feel that the gripped body is much better balanced. The larger profile makes that camera easier to grip, hence it is called as such. Lastly, there is the additional shutter button, so you can shoot more easily in portrait orientation.
I'm looking forward to the rumored 5Diii because the grip shows a joystick on it. Who knows if 3rd party manufacturers would get a joystick right on a grip. I'd get a Canon for that reason alone. The joystick rocks.