As a NASS detailer from last summer, I can say that we definitely appreciate those who put out the extra effort all the time. I personally think there's nothing wrong with being bothered by others being lazy and not taking advantage of the great opportunity to learn and strut their stuff (we wrote reports on all candidates that came through) -- that just shows you have a work ethic. At the same time, you don't want to complain, come off as cocky or throw anybody under the bus. Just work hard, have fun, and do your own thing, and you'll learn a lot and have a great time.
NASS PT isn't really that difficult at all. The morning workouts are shorter and a little easier than those you'll do at the start of plebe summer (which aren't hard either), but the one morning with Stew Smith will be a kick in the butt if you aren't good at pushups. The part that most candidates had trouble with was the mock sea trials; it's only six hours long, but it is very hot and humid out and you'll be running a lot while losing lots of water.
You'll have a great time at NASS. Just go in with a good attitude and make an effort to be on time to everything.