Robert
I have had a 28 - 105 for about 4 years and a great lens it is too.
I bought the D70 kit lens as I need the '18' for the house
internals I shoot. Ideally I would like the 12 - 24 but that will
have to wait until the pockets fill up a bit.
The kit lens is very nicely balanced with the D70 camera and very
good value when bought as a kit. Image wise I am very happy with
sharp images across the board, however using it wide open at 18mm
is best avoided due to slight vignetting. For Aus $250 you can't
do better.
I think the two lens' complement each other quite well and are of
very similar quality, if you are happy with the 28 - 105 you will
like the 18 - 70 for sure.
If you have sufficient $$$ then perhaps go for the 12 - 24mm as
that would widen your scope.
Andy Warren