Depends on how close you are -- I went to the Vegas race a couple of years ago and was in the infield and was right up against the fence and though you couldn't have a conversation with anyone -- it wasn't any louder then any rock show I have been too.
Seeing a race LIVE I think at any track is difficult to see. We timed it so I could get some photos of Dale Jr.'s car and they came around every 29 seconds. That's all I could see where I was at. It is best to be by a monitor or get high enough so you can see the entire track. I didn't have a bad time even though I only saw the cars every 29 seconds -- it's a cool experience. We only encountered one butthead the entire time -- everyone else was real nice.
Like everyone else said -- bring a lot of money (parking, headsets, food, etc.), sunscreen, a hat, etc.