I've only been here once, for the Coca Cola 600 in 2011. My friends and I got Hot Passes, so my experience is not the usual.
Watching from either the grandstands or at the edge of the infield is cool because you can hear and smell and feel the cars go by and it's amazing. However, watching the entire race from there could get a little boring. The giant HD screen can help your understanding of what's actually going on from either location.
You can bring in your own food or beer, which is AWESOME.
Also, I went to the dirt track across the street for a race that Saturday night and would VERY HIGHLY recommend it to anyone. It's a smaller, more intimate experience. It's fun watching the cars slide around the corner and there were many wrecks (which did make it take forever). Just know, going in, that you're will be covered in dirt by the end of the night (and bring glasses to protect your eyes).
Everyone was very friendly and the fact that you can bring in your own food and drink really make the track a fun weekend.