1. Huntington Station is a miserable place to commute from - there will (outside of pandemics) never be enough parking capacity, even the brand new elevators will likely be poorly maintained and once again become vertically mobile cesspools. And if you've ever had the fun of arriving there homebound in rush hour, it's beyond insane getting out of the garages and parking lots unless you park far out.
2. It takes time to get there - at rush hour coming home at least 30 minutes for me. Kind of defeats the idea of commuting on a train if you then have a long drive to get home. Morning is no better.
3. Stony Brook University - they get minimal east bound service AM, same west bound PM. Unless you have a car, makes for a miserable commute.
4. It is a miserably slow line - same sort of performance as depicted in the several decades show Petticoat Junction (actually, I think that was faster). So in the city, you may have a series of subway car rides to get to Penn, or one of these decades GCT. If GCT, somewhere unknown at this time you will transfer to a diesel - or maybe an electric and then again to a diesel. On one electric diesel combo today from NYP, takes 90 minutes on a good day to do the 40 miles just to East Northport, add 10 or 15 for Smithtown, etc. Gets to be a very long commute. And again, driving to Huntington gets less and less viable the farther out you are - Greenlawn is maybe OK depending on timing.
5. You are right about it not really being farm country (a reminder of the insanity of Mr. D's comments to me all those years ago). Unless, of course, you get far enough past Pt. Jeff Station and onto the North Fork.
The PJ line is full of at grade crossings, slow curves - it reminds me of the lines used by excursion trains at rail museums. The equipment was junk when it went into service, appears to have been poorly maintained from day 1, with frequent breakdowns in cars and locos. And there isn't anywhere near enough of it. The line needs to be double tracked wherever practical (should be end to end) and electrified, and grade crossing elimination prioritized (cut down the death rate). And if I could, I'd have it re-extended to Wading River and beyond to meetup with whichever other LIRR line is close enough.