What you see through the lens IS what will end up in the photo. Yes pro bodies offer the 100% viewfinder instead of the 95-98% of consumer cameras. That isn't related to the crop factor, but is actually an issue even with consumer grade films SLR's like the N80. For the casual photographer this isn't an issue. The crop factor is an issue, if you plan to use only your older lenses. They will work fine, but your 28-80 lens will now be the same as 42-120 on film, 70-200 now becomes 105-300mm. Yes it is even with the bundled lenses, the 18-55, becomes 27-83mm(close to the 28-80 standard zoom for film).
One other thing to think about with the older lenses... Generally the cheaper, consumer grade lenses, ON FILM, are going to be sharp in the center and may be rather soft around the edges of the glass. This causes the borders and corners of photos to not be as sharp as center. With the older lenses on you "cropped" DSLR, the image is resolved by the centermost, and sharpest part of the lens. So basically, don't let this crop factor thing be a barrier to buying a DSLR. You may want to soon add a wide zoom of some sort, like a Nikon 18-55, 18-70, 18-135, to cover what would have been the 28-40mm wide end of you film range.