No. A 50mm lens is always a 50mm lens not matter what body you attach it too. What does happen is that the field of view varies depending on the size of the sensor. On cameras with the smaller sensors, everything except D3, D3x and D700, the FOV is the same as a 75mm lens on a full frame camera, but the depth of field is still that of a 50mm lens, that is deeper than a 75mm lens would be.
The biggest difference will be image quality. The 50mm f/1.8 is a very sharp lens, considerably better than the 28-80. The other difference is speed. The 50mm f/1.8 is about 2 fulls stops faster than the 28mm end of the zoom and probably even more than 2 stops at 50mm. Two stops is 4X as much light.
When trying it out, keep in mind that if you shoot wide open at 1.8, you have a lot less depth of field. Some people mistake the out of focus areas for poor lens performance. Wide open is good for isolating your subject from its surroundings. For other shots, like landscapes or travel when you want everything in focus, be sure to stop down to f8 or more.
For the price, the 50mm 1.8 is a great performer and value. I have one in my bag.