I have the 24-70 f2.8, 28-300 and 16-35mm f4 (amongst others). Of course the 24-70mm is fantastic, the 16-35mm a very capable lens too. However, I find myself with the 28-300mm mounted most of the time and all the time when travelling. Yes, it's heavy but balances very well on my D700 + grip. I've mentioned elsewhere how suprised I am with the IQ, however that said at 300mm it's not equal in my opinion to the 70-300mm, it's a bit soft. One can't have everything, but the 28-300mm gives me most of it. I did have the 24-120mm but only the older version, that said it was a very capable walkabout lens, despite much bad press. Personally, I prefer heavier to lighter lenses on my D700.
I tend to keep my 24-70, 16-35 and 70-200mm for when I am out doing competition photography and for those landscapes I print to 16x12 inch for selling.