The 18-70 Nikkor is an excellent, lightweight, and compact mid-range "prosumer" zoom lens, with superb optics for its class, and fast AFS focusing as well. It is an official Nikon lens. I replaced my 28-105 Nikkor (another excellent affordable optic) with the 18-70 just a few weeks ago. This focal length range is well matched to the Nikon DSLRs, giving you an equivalent field of view of 27-105mm in 35 mm format, which is exactly what I had before with the 28-105 and an N80. The only downside of the lens compared to the 28-105 is slightly more barrel distortion at short focal lengths, and no 1:2 macro function. This lens would be a good place to start with a new D70 or D100, unless you want pro zoom glass, which is typically f/2.8 constant, and a lot more expensive (and heavy).

Cheers.