The Nikkor 24-70 mm f/2.8G is for sure a fine lens. But the Tamron 24-70 mm f/2.8 is rated (by DXOMark) higher than the Nikkor both in overall performance and sharpness, is a bit smaller and lighter, has vibration compensation, and costs about $600 less.

The 24-70 mm f/2.8s are quite huge and heavy though. A lot of folks like the 24-120 mm and 24-85 mm offerings for a general purpose lens, smaller and lighter, wider zoom range, although you give up about 1/2 stop in maximum aperture. I have the older 24-85 mm f/3.5-4.5 ED-IF non VR version. It is fairly small and lightweight, makes a great walk around lens, and DXOMark rates it only 1 point behind the Nikkor in sharpness. They run $225-$275 on Ebay.

All that said, if money was no object I'd buy the Nikkor 24-70 mm f/2.8 but still use the 24-85 mm as my walk around lens.

First, the D610 is a great choice. If the D600 had been available at the same time as the D800, it would have been a tough decision for me.
Since you have both the 18-200mm and the 70-200mm, and you are using the 70-200mm the most, it sounds like you're really not getting into the 18-50mm DX range, which is what the 24-70mm FX would give you. I understand being a left-brainer, but that means that 24-70 is especially boring. It seems like the 70-200mm would be fine until you spring for an exotic telephoto. ;-)

If you're really worried about having nothing below 70mm, get the new 18-35mm f/3.5-4.5 ($750), less than half the price of the 24-70mm ($1900). I really don't think you'd feel the 35-70mm gap, but if you're also worried about that, get the Nikon AF 50mm f/1.8D ($120), and you're still under half the price of the 24-70mm.

The worst feeling is spending $2k on a lens you never use, especially when you know it's a really good lens, but doesn't fit your shooting needs.