Ha!
Thinking of those guys saying that the focal length of this lens is reduced considerably when focusing close, I just tried the same close-up lens with the 18-200 Nikkor zoomed out to 200mm BUT with the focus at infinity.
Guess what happens: I get a reproduction rate of nearly 1:1!
This one is really wild: While you focus closer the repro-rate is reduced
It's easy to understand once you have accepted that at the closest focussing distance of the 18-200mm Nikkor at 200mm (approx. 50cm) the focal length of the lens is only about 65mm!
So you can get pretty close to 1:1 repro-rate with a +4 close-up lens, but don't forget to focus to infinity!

_________________
Thomas (beware: Nikon-fanboy and moderator!)
My Lens Reviews,
My Pictures,
My Photography BlogD800+assorted lenses