I am seriously thinking about upgrading my D90 for a D7100, it's just a matter of raising the funds which is not easy on a pension. I currently use a 16-85 as my "normal" lens, and also have a mint, boxed 35mm. 1.8 AF-S which I never use. Would I be mad to swap the 35mm for a similar condition 18-105, and then sell the 16-85? I know what is said about glass but I don't think I would notice the difference in quality in the type of pictures I take.