Let's check it out. Assuming that:
» Your 18-55mm VR is in good enough condition you can get $100 for it.
» You can find a used 18-70mm for $200.

You would gain 15mm on the long end.
You would gain speed on the long end.
You would gain build quality.
You would gain manual focus override.
You would gain size.
You would gain weight. (!)
You would gain a /marginal/ amount of image quality, unnoticable in the field.

You would lose VR!
You would lose your filters! (58mm vs 67mm)
You would lose $100!

Since I spend most of my time on the long end and don't use VR I say it is worth the $100 for me to switch. I would not be surprised if others found the pro's meaningless. My real question is, how hard would it be to sell my 18-55 for $100? It seems to be the asking price on eBay.

Maybe purists would find it more appealing to switch to a 35mm 1.8 G

Experiences and thoughts welcome, thanks!