They are all like toy, the 18-70mm is no exception. The zoom ring is sticky and inaccurate, but the focusing ring is smooth. You are only paying for the optics on these lenses, the build quality is toy-like.

The D70's standard lens is the 18-70mm. You sure you don't have that already? To achieve a nice background blur, u need to have a rather long subject to background distance, and u need to shoot at large aperture/long focal length. It has nothing to do with whether the camera can do it or not, it depends on those aspects i mentioned.

Sorry for my ignorance, I read the thread again and noticed you said you have the 18-135mm.

If you already have the lens, you can just stick to it and forget about the 18-70mm. The optics are quite similar with the 18-70mm having a small edge in IQ. If you plan to get the 70-300mm (get the VR, don't waste your time and $$ on the non VR version), and IF you can get a good price for your 18-135mm, then I'd suggest you sell it and grab the 18-70mm and use the extra funds from the sale towards the 70-30mm vr. However, if you cannot get the 18-70mm + $$ for your 18-135mm, then I'd suggest you just stick to what you have until you can afford some of the better lenses.