I got NPQed from 187, so I've got some fresh insights, at least on the first 3-4 weeks. My platoon had less than 10 priors out of 61. 4th platoon next door had 20, I believe. Some of our priors were f'ing locked on and were great leaders. Some of them, you might never know that they were priors, but were not too bad if you got to know them or when they were billet holders. None of them were projects, but they got extra reamings around inspection time for not squaring away their platoon.
We had one prior that actually freakin passed the first inspection - the one that no one is supposed to pass. The staff were hella pissed, but not because he ruined their fun. Rather, they gave him the hardest reaming, because our platoon was crazy jacked up and he hadn't spent any time squaring away even his rackmate (they actually yelled at him for his rackmate's failures instead of the joker who forgot to fill his canteens and such).
The PT really wasn't bad at all for the first 3-4 weeks. I'm no PT stud on the running (which is the most important by far), but I trained 6 days a week before going. My body was used to much worse than they were throwing at me. It is true that injuries are hard to heal, and a cough that you get in the first week will stay with you until you get home.
Oh, and one of our best candidates was 32 yr old prior grunt. Our platoon staff didn't do what everyone said they would - give the first billets to priors. They gave unofficial (meaning they didn't get evals for it) to priors at the VERY beginning, but our first candidate staff was one prior in pltn sgt billet, and 5 non-prior squirts (including myself as squad leader) in what I can only guess was an attempt to show the platoon what a god awful train wreck a weak candidate staff can create.
If you get an early billet, as a prior or not, it is your job to set up a system for future candidate staff and for your platoon to function properly. That means, you will have to figure out a way to get all the cleaning done as automatically as possible (i.e. without doing it by the numbers) before lights. Having a clean house and getting your counts right all day are the absolute most important things you can do in a billet position. Do not ignore these responsibilities in favor of any bright ideas that may come into your head.