Trichinosis is generally found in garbage fed hogs. It was a common practice a hundred years ago but is rarely done now. To me, a feral hog is essentially a free range hog without an owner.
I've eaten many. The really big ones are generally older and make poor choice for hams, chops etc, but can make really good sausage especially if mixed with ground venison. The smaller ones, under 150 lbs are delicious tender meat but the the chops are really tiny. Some years, with a good acorn mast they will get really fat and tender.
I avoid eating boars over 120 lbs or so as boar meat has an offensive taste and smell to me. Many folks make really hot and spicy sausage with them and I've heard its quite good.
Some local hunters started releasing hogs on federal land here about 20 years ago or so and they have become a serious problem now. I'd like to see them all gone.