Well, I only have 3 DX lenses right now (35mm f/1.8, 40mm f/2.8 macro and Sigma 17-50 f/2.8 ) and don't use the 40mm macro that often. My other lenses are FX (50mm f/1.8, 85mm f/1.8, Tamron 70-300 VC, and Tokina 100mm 2.8 macro).
So I would mostly just be missing a fast zoom. I probably wouldn't try to replace that, at least right away since FX fast zooms seem to be a bit pricey. I suppose I could use Sigma 17-50 f/2.8 in crop mode on the D610 for those times I wanted to carry around a zoom. I assume that would work just as well as on the D90 but that is just a guess.
I would seriously think about getting the Sigma 35 f/1.4 that Haj mentioned though.