Has anyone done this before and if so how was it? Looks like a decent deal - $30 and you get a spot plus access to the high school showers, bathrooms etc. Plus it's pretty close to the shuttle. Obvioulsy much cheaper than any hotel option down there, especially just for one night.
But, before I send in my money for it, is there anything I should know? (coming from a VERY inexperienced camper!)
I've done it a couple of times and, for what it is, it's fine. The things to look out for are that you'll want to pick a spot as far from the road as possible. No matter what, you're on a pretty busy road and every time I've camped there, about 2-3am the drunks are heading home from the bars and generally there is lots of honking, yelling, etc. It'll keep you awake if you don't take some ear plugs.
Also, it can be very hot. Both times I've camped it has rained/thunderstormed at night so I had to use the rainfly which trapped all of the heat in the tent. I think this was just bad luck on my part. Probably not typical but something to be prepared for.
If you do camp and are taking your own car, don't mess with the shuttle. There is plenty of parking... just drive over.
While camping isn't ideal from a rest standpoint, it is close to the start and it's cheap. And those were always priorities when I did it. It's an expensive race so you might as well shave costs where you can. You should just make sure to get plenty of sleep leading up to the race and you'll be fine if you don't sleep well the night before.
I hope that helps.