I had the 18-105mm for about a month, along with the 18-55mm at the same time.
I'd say that they 18-55mm was a *tiny* bit sharper at 30-45mm and f/8. I'd say the 18-105mm was a bit sharper from 50-55mm and f/8. Everything else was pretty close to equal.
the thing I didn't like about the 18-105mm from 55-105mm is that it wasn't really good at anything. It wasn't really fast enough for most wildlife, unless you got the animal just perfectly still and could snap a long exposure, or were in borad daylight (and if you're in broad daylight shooting wlidlife, why are you in broad daylight shooting wildlife?) the DOF control wasn't really good enough for portraits in that range, IMHO. Most everything I used from 55mm and up on it, honestly I would have gotten about as good of an image just cropping from 50-55mm.
Essentially, I found that from 55-105mm, the thing just wasn't good enough to warrant paying more to 'upgrade' to it. It's not a bad lens, by any means, but unless you are constantly needing to go from 30mm to 105mm, it's not really good enough at any one thing to view it as an upgrade. It's a great starter lens if you get it in your kit with your D7000, but that's what it is. I don't really see a need to ever go out and buy it unless you just get an outstanding deal and still feel you are in the 'beginner' phase. Your best bet is to find somebody who just upgraded all their glass on their D7000 and then talk to them about all of its shortcomings (which they will be very aware of) and convince them they don't need it any more. I did that, got it for a song, and I still found no use for it, lol.