You get a 3 day weekend after orientation & before class starts. 😛
Here's a comparison - with car insurance, the minimum is liability only, right? So if you do have an accident, you pay a bunch out of pocket. Full coverage would cover everything, with a deductible, and may cover ancillary things like glass.
The insurance they are referring to as "disaster insurance" is more like liability only car insurance. It has a low per-month cost, but it (typically) only covers after you hit a high out of pocket maximum, then it might share the cost. Basically, if you have to be hospitalized, it will help, but anything short of that you're paying for yourself. The gamble is that you won't need any other sort of healthcare (say, if you catch strep throat). The last time I had the option to buy this sort of health insurance was some time ago, so I don't know how the preventative care mandates play into disaster insurance.
The insurance you'd be purchasing as a student is a little under $200 per month - I think I worked it out to about $2,000 a year. It's more like "full coverage" - many services are covered, with a deductible or copay. It's an Aetna plan, and there was some sort of interplay with the on-site clinic - I thought maybe I read you were required to go there first or something? Anyway, it covers going to the doctor to get a physical, or if you get strep throat, or if you have to go to the ER. The student plan is actually relatively affordable as far as health insurance goes. For comparison, I had an Aetna plan in 2011 and I paid a bit more per month through my employer ($20-40). I have worse insurance in 2012 and I still pay about the same amount. And my employer has pretty good benefits. Reason being, students are usually relatively young and have fewer costly ongoing health issues, so it's cheaper to insure them as a group.
The reasons I can see you might not want to go with the school's plan are if you are covered under a parent or if you are otherwise already covered, like by a government agency (the VA or IHS).
I'm pretty sure this is how it works - that the cost to cover the health insurance is included in your student aid package, but if you're otherwise covered, you can waive out of it.