Haydn, To share my experience, which will echo what Rick, Mick and some others said, my D800 was my first Nikon DSLR. I picked up a couple of used Nikon consumer zoom level lenses to start with, because that was all I could afford. The images I got with the D800 made their weaknesses readily apparent, but this was an excellent first-hand learning experience for me. When Nikon put their new 24-120 4.0 on sale last spring, I snatched one up. And I love it! From my experience with cheaper lenses, one of which was an earlier version of the 24-120, I am thrilled with what the new lens does.
For now, that range is fine for me. I haven't taken it off the camera in months, and most of the time I have that combo slung over my shoulder every where I go, and my camera bag stays home. And I am having fun! With this lens and my D800, I am really enjoying photography like never before. The 36 mp images allow a whole of of cropping most of the time, so the reach of the lens is actually more than the 120 might suggest.
I do have plans for expanding my lens collection in the future, especially on the longer telephoto side, but for now I am having a blast learning the D800's capabilities, and photography in general. Spending a lot more money on lenses has become much less of an immediate priority for me.
The new 24-120 is by no means cheap, it's a pro level lens, but you can get a whole lot of bang for your buck with it.