I know this is an answer to an old question, but my response may be helpful to others who come here later. I recently picked up a very clean 35-70 f2.8D for the grand sum of $200, which included shipping and the Nikon lens hood. I also at the same time picked up a 24mm f2.8D from Japan, mint in box for $125. My thought was to use the 35-70 on camera, and carry the 24mm in a pocket to use when 35mm isn't wide enough. This combination is within one ounce of the weight of the 24-70 2.8 Nikon zoom and costs $1,000 less when comparing clean used lenses. At an event, I'm also carrying about ten ounces less around my neck compared to the 24-70.
I'm really happy with this combination on my D700 and my D600 in real picture taking. Honestly, the 24mm wide open is weaker in the corners than the 24mm setting of the 24-70mm zoom wide open that I have borrowed from my friend. Other than that, I can't see a difference that matters to me. The "push-pull" zoom is not my favorite, but for a thousand bucks saved, I'll live with it.
In terms of image quality and sharpness, the 24mp sensor of my D600, when I look at 100% and really pixel peep, I see a very slight improvement in favor of the 24-70 in terms of sharpness over the 35-70 in their shared focal length range that has yet to manifest itself in any real way in the photos I take or print, which are usually no larger than 20x30. The 35-70 gets a very, very slight boost in sharpness when stopping down from f2.8 to f4 if you are pixel peeping, but it is excellent at 2.8 and the difference almost isn't worth mentioning. Stopping down further yields no additional improvement that I can see. There may be some differences on a 36 mp sensor, but I don't know. Color rendition between the two lenses seems identical. The 35-70 has less distortion than the 24-70 at the wide end, but distortion is usually correctable later on.
Focus speed seems about the same between the 24-70 and the 35-70 to me, although the 24-70 is almost completely silent. Neither is objectionable though, even for quiet environments like a wedding ceremony. Another plus in favor of the 35-70 is that there is not AF-S motor to ever have to replace. On an unrelated note, the 35-70 retains an aperture ring, making it useful for manual focus film cameras. This was a concern for me because I still shoot those.
On the downside, the 35-70 is not at all happy being shot into the sun or a light source, flare is an issue even with a lens hood. Since I use this primarily for indoor events, this is of little concern to me, but may be significant to others. The 24-70 seems better in this regard.
Hope that helps.