Not sure if this is the first post, but there seems to have been little interest in the grip, but I have a couple of questions, one of which will probably not be answered until it goes on sale.
First one is that it seems from the pics of the alloy shell that the batteries will go in from the side like the 1D series instead of from the back in the BG-E6. If this is the case then the batteries will need a carrier, but I do wonder why a battery grip couldn't have the NP-E3 type battery pack of the 1D series?
The second is the issue that the battery grip has had with compromising the weather sealing, not just on the 5D MkII but others when water entered through the cameras battery compartment. I doubt anyone can answer this unless Canon has mentioned it or they've asked a rep.
I like a battery grip, it makes the camera much easier for me in portrait, especially with an extra set of controls.