Lens advise for new D5100???

I have a d700 and a d800 with the 24-70 and 70-200 nikon lens plus a macro and the nikon 300f4 and the 17-35 lens.

I just got a new d5100 as a walk about every day camera as the above outfits are too heavy for me to carry for any length of time.

The camera came with the kit 18-55 lens and I am really struggling with the quality of the shots from it. I do have the good glass as above and the quality using those on the d5100 is good but I want a light lens. Is the Nikon 18-200 any good on the d5100 and is it a light combo?

If not what other good quality walkabout lens could I go for that is light besides a prime.

Thanks for any help or advise.