I use the Tamron 90 mm macro exclusively for my shots on my Nikon D300 and love the lens. However, if you are looking for it to autofocus on the D3000, it may not do it as the new Nikon D3000 has to have a motor in the lens to autofocus.

Having noted this, I can say that most of my macro pictures are focused in manual mode anyway. Here is a good writeup on the lens.