I was recently shopping for a macro lens in Nikon mount in the 150-200 mm range and along the wway I stumbled across a lot of very positive comments about the Tamron 90mm macro. It certainly appears to have a lot of very well satisfied users.
I look for macro lens short time ago. I choose two of them one for myself and second for my frend. For myself i decided for Nikkor 40mm/2.8. But for me the price was very important. (In Poland it is half a price of any other, and this lens still have good reviews). Second i choose Tamron 90mm. It has good price, and very good review. The only disadvantage is "loudly and slow AF", but if it is really mcaro lens it's not so important. The same with the Sigma 105mm/2.8. You can see the photos from the two test: Tamron: [link] Sigma: [link] My frend said that he like this Tamron lens But... It's hard to say which is better when you have no possibilities to try first and second one.