It depends on a lot on your needs. If you need a lens that can produce a shallow DOF or for use in low light situations, then its worth getting. If you don't have any intended use for this lens, then its not worth getting.
What else do you know besides..you want a lens that gives you better pictures.
btw..like other mentioned. Lens technically dont give you better picture..but they can give you sharper picture..
For better picture..its up to you.
Just got my first prime AF-D 50mm f1.8 last week. It is cheapest nikkor lens and good enough for portrait for beginner like me, I think. IQ also not bad at all at its price range. For low light condition, I'm satisfied with that lens too. Like all the people said, whether better picture or not is up to the photograpger of course. But again, it is worth getting anyway.
50mm lens have better resolving power, can produce better images in term of sharpness and colors,
and it has larger aperture, you can get narrower depth of field and able to shoot at higher shutter speed or larger aperture compare to kit lens.
Dun buy the lens because it is inexpensive. Buy it only if you know you need it.
50mm is inexpensive and can take really nice portraits with nice bokeh (for the price you pay). But how often do you take portraits (as in half-body or just head shot)? If it's very often, then it's a good lens for you. If no, then probably you may want to consider other lenses (for eg 35mm, etc). If you are using a cropped body, the FOV is narrow and using the 50mm lens can be quite challenging at times especially indoor.
First, got to ask yourself on what is your photography style, using it like a compact? Mainly groups at the outdoors in the day?
If you're using it as a general lens, the kit should fulfill most of your requirement and also give you the versatility with the zoom. When shooting out doors in the day (where you're not too concern about bokeh), both the Kit lens and the 50mm may be almost on par unless you really enlarge and scrutinise all the corners.
The difference will be more obvious when the lighting is low, undeniable that the 50mm will stand out better in the IQ. Good or bad pix may depend on the photographer....BUT, the difference is a BETTER bad image, or a WORSE bad image...:bsmilie:
If want to take the first step into something of a more refined photography, and don't mind the restriction of a fixed 50mm, then you can seriously consider one for use whenever opportunity arise.....