Got my 6D the other day and the only thing i'm disappointed so far it's the ergonomics and the cheap feel of the body and buttons. It simply doesn't compare with my 5D II. Ofcourse i was not expecting the same build quality as the 5DII ( that's 5D3 territory) but i was expecting something better than this.
I plan getting the battery grip, hopefully the extra size will help balance out my 70-200
I have a Meike battery grip, and I like it pretty well. No doubt it pales by comparison to the Canon one, but at 1/4 the price, I can more than live with that. It feels a lot less solid than the body alone, but the grip itself is very nice when you need to shoot in portrait mode. I actually have mostly only used it with the one battery, rather than two...so the weight/balance isn't as ideal as with two batteries. I still enjoy using it on occasion, when the need arises.
As for your opinion of the lack of solidity, I disagree. I've tried a 5D2 in the past. It's simply a matter of the amount of force it takes to press buttons and move dials. With the 6D, they wanted less force applied, and I happen to like that decision. It feels no less solid to me. The clicks of the dials feel very snappy and definite. Certainly it makes the 5D2 and 5D3 feel like bricks by comparison, but if that's what you want, you should have bought the 5D3. Weight does not equal rigidity, though...not at all. Not saying the 6D is more rigid, just saying rigidity is not its problem.
Specifically on the feel of the shutter button, I happen to like the feel of the 6D's better than all other Canon cameras I've owned, rented, or tried including an older Rebel, a 50D, 60D, 7D, 5D2, 5D3, 1D4, 1Ds3, and 1DX. Worst of all, at least to my memory, was the shutter button of the 7D, with the 5D3 being very similar. Far too mushy and no transition between half pressing and fully depressed. Hopefully they will fix this with the 5D4.