Not to toss a lot of dissent into the mix, but I've tried the 24-120 VR and I consider it to be a poor performer, even on a DX body. I'd say it performs about like the 28-80 G.
If you're considering the 24-120 VR, save yourself a lot of aggravation and go to the 24-85 f/3.5-4.5 AF-S for a decent lens on a DX format body or keep what you have. The 18-70 out performs the 24-120 hands down. Another decent option is the Tamron 28-75 f/2.8 for around $300 it's respectable though it's build doesn't stand up to heavy and hard use.
Here's a review by Thom Hogan.
Nikon 24-120mm AF-S VR Nikkor review by Thom Hogan
Here's the review on the 24-85 AF-S
http://bythom.com/2485lens.htm
and his review on the 18-200 VR
http://bythom.com/18200lens.htm
I'd strongly urge you to try to read up on user experiences online and perhaps try some of the options at retail stores if possible. No one likes buying lenses twice and at the prices of today's Nikkors, buying and trying is going to be far more costly to you ... especially given the latest economic conditions.
Good luck!
Julio