The Vivitar Series 1 28-90 f/2.8-3.5, is a very good lens. Also, the Kiron 28-105 f/3.2-4.5 is very good, built better, and is faster & sharper than the Nikon 28-105 offering. I'm not bashing the Nikkor's, I love them. But there are third party equivalents, that are as good or better, at a fraction of the Nikkor's cost.

Kiron Kid