I've heard good things about the 200mm Nikon macro lens too, but cannot comment on it from personal experience.
I use both the Nikon AF-S 105/2.8G VR and the Sigma 150/2.8 APO macro (non-stabilized version).
The 200mm should offer the greatest working distance of all these, the 105 VR offers 15cm @ 1:1 and 34cm at 1:3 magnification, the 150mm Sigma has 20cm @ 1:1 and 45cm at 1:3. For more details see my review here
Btw.: If you're not necessarily into 1:1 range a very comfortable working distance could be achieved with an old (and discontinued) Sigma 300/4.0: it offers 1:3 magnification at a working distance of around 1m! Some of those old lenses can still be bought used.
Thomas (beware: Nikon-fanboy and moderator!) My Lens Reviews
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