Hi,
We've flown with Spirit several times out of Atlantic City, with no problems whatsoever.
The airport is less "hectic" compared to Philly, as it's much smaller. We flew after all the 9/11 restrictions, and unless it's changed, you can pull up to the terminal and unload luggage & your party, then zip right over and park the car.
Nothing fancy, just a big paved lot (used to be a big dirt lot, no so long ago,lol).
Because we've always had good experiences with Spirit, I'd be willing to pay a little extra to fly with them rather than leave from Philly, but Southwest's fares have always been much lower for our travel dates for the last couple of years.
-Mark