I hate to be the pedantic a**hole, but DX does not give you 1.5x zoom, it gives you 1.5x crop. A FX camera with the same pixel density as your DX camera would have the same resolution (pixels per degree) as your current setup. As the technology starts to mature (in so far as densities) I expect FX and DX sensors to plateau at around the same density, making this pedantic point all the more clear.
No where have I stated that DX gives 1.5 Zoom, but at the moment special in entry DSLR you get effective mm, right, what you see in your viewfinder. A 50mm lens on a DX will give you angle view of app 75mm if seen through a FX camera. If a customer walks in with a F80 and his 28-80mm lens and don't want a D700, what should I tell him that his 28-80mm lens is going to do on his new D90, should tell him that he would end up with app a (effective) 42-120mm lens, because if I do not get him to walk home with a 18-105mm zoom(or similar) he will back the next day telling me what is going on, I can hardly shoot any pictures inside now
Yes I know this argument will newer end or be won.
Why else would you purchase a new 35F1.8 DX lens, because it shoots the same way like a 50mm does on DX, yes DOF is different, but the angle and what is seen in the viewfinder is certainly very similar(and that is what's count the most