Thanks, everyone. I did have the 24-120 f4, but found corner sharpness (at least in the one I had) somewhat lacking. On the D700 it was good and the extra reach over the 24-85 was welcome, but the D800 showed its failings.
I shoot landscapes mostly with my 50mm (it's light) or the 17-35 f2.8, which is superbly sharp (it replaced my Zeiss 25mm) but rather heavy. I could do with some extra reach at times though, and in bad weather, I'd prefer not to have to switch lenses, hence the interest in a new standard zoom. I'd also like to use it for more general use, travel, covering events and the like, where I also don't want to keep swapping the lens.
Maybe I should try another 24-120 or save for the 24-70 2.8E