OK here's my 2 cents. I have the macro lenses and they work, but I only use them for close up pictures of stuff I sell on eBay. Never tried them for anything else.
As pointed out, they are extra glass in front of your lense and by that I mean a LOT glass. The +10 is very thick.

I just won a Kenko set of Macro Tubes on eBay for $125. There's no glass and this set will allow all the auto functions of your camera and lens. Of course I haven't received the set yet so I don't know how they'll work, but I'm expecting they'll be pretty good until I can afford a macro lens.

Also, I'm pretty sure my 55-300 mm Nikkor kit lens has a macro function, but that may be a function of the camera.

So, there's some more options to mull until you get that macro lens.
HTH

Yes, the FX lenses are all fully functional on the D90 and D7000. Also on the D50, D70 and D80 models. There is no functional differences between FX and DX type lenses. The DX lenses are lighter and smaller due the being made for the crop sensor bodies. This allows manufacturers to use smaller glass elements inside the lens barrel and save money in the manufacturing process. Notice the FX lenses are not marked FX, they are Standard lenses. DX lenses need to have the DX designation to let all users know they will not give desired results on a full-frame body. DX lenses will still mount and function properly on a FX body, but the image projected on the sensor will not cover the sensors area and will result in a photo that is smaller than the cameras capability. It will have a black area all around the exposed image where no image was projected. Nikons Full Frame DSLRs have the ability, either manually or automatically, to shoot in DX mode to eliminate this black area and only show the resulting DX size image. But this will also cause a 12MP D3 for instance, to take a 6MP image.
Clear as mud???

Those DX lenses just are not made to work PROPERLY on the FX body do they? I shoot all FX lenses on my DX bodies in the hope of someday upgrading to a pair of FX bodies, if and when the checking account allows it. Only DX lens I own is a 18-55mm VR kit lens because it was free. For now, the D7000 produces wonderful results and I am happy to be shooting with it as well as the D90.