The experience will help as far as your clinical skills. You will also begin to feel more comfortable going into a patients room, and touching them. That is normally a first fear to get over, and being a CNA will help with that.
I was a CNA before I started college, and it about made me quit nursing all together. It is not great money (I made 7 an hour in Illinois). It is very hard, and mostly the dirty work. Keep in mind that nursing is not all about bed pans and attends. You will learn many skills in school, and when you graduate, you will be doing much much more than toileting. This is not to offend anyone, CNA or otherwise, but CNAs often have to do the really "nasty" stuff that many nurses will not do. If you are lucky, you will work with Nurses that still remember that patient care is part of their jobs too, and will not ask you to do anything that they would not do themselves. But, many CNAs become the go-fers, and can be abused by nurses on the floors.
Being a CNA will definately make you a little more aware of what the job they do is all about, and will REALLY make you appreciate them in a whole different light. Good CNAs are hard to find here in my area, and the good ones we have, I treasure! I also have learned many neat things from them, (like smearing vicks vapor rub on my upper lip before going into a really smelly room if my stomach is upset), that have made my clinical rotations much more pleasant.