5D3 grip - solid??
The connection between grip and body is very solid and the combination feels like a single unit. Shooting in portrait mode is very comfortable - much more so than the 5D Mk II/grip combination.
The only downside is that the 5D MkIII/grip feels heavier than the Mk II combo. I actually haven't weighed them, but it definitely feels weightier. So much so that I am not looking forward to the effect that the RRS L-bracket will have on it. Not sure how this all compares with a 1 series, as I have not used one in a while.
Bottom line is that, regardless of the weight issue, the combo is well worth it to me just for ease and comfort of the portrait mode shooting.