the Sigma 105mm f/2.8 EX DG Macro Lens

Hi guys,
wanted a few reviews for the sigma macro 105mm lens as compared to the 105mm nikkor.....and also needed to know if vivitar manufactures ring flashes that are custom made for the sigma 105mm DG macro and the price for such a ring flash as the sigma ring flashes is a bit steep on my budget......
oh i should be getting a Nikon D80....oh the sigma macro is compatible with the nikon right?
shall wait for reviews on the macro lens
thanks

I bought the Nikon 105mm, never looked back, spend more get more, I have only 1 non-Nikon lens a Sigma 24-60mm 2.8, takes nice shots. If it's portrait work and macro work then run with the Nikon.