Smithsonian Magazine just had an extensive article on the spread and destruction of feral pigs - very interesting info there.
I live about five hours north of San Francisco and there are areas east of the HWY 101 where the pigs are well established and they can be very destructive. What others have said before me is true - they can plow up a large area of ground in a single night. Pigs are resourceful, very smart, and they reproduce almost like rabbits, so yes they are formidable in their destructive ability.
I went out pig hunting several weeks ago with my .54 Investarms Hawken into an area that was just rank with fresh pig sign, and I had a chance of shooting an enormous sow at 30 yards but the light was just dim enough where she stood under the trees that I could not tell exactly where the sights were lined up, so I did not take the shot. She looked in my direction, wiggled her ears in a very comical fashion and trotted away. Dangit, I had been taking photos of my hunt and was hoping to share the story and its successful conclusion with everyone on this forum, but it was not to be.
Two weeks ago however I managed to kill a 200 lb boar with bow and arrow, so now my freezer runneth over.
A .50 or .54 etc will certainly be enough for wild pig. For a sow or smallish boar I would even venture to say a .45 would be enough, with correct shot placement and within the effective range of the caliber. If you keep the wind in your favor you can stalk very very close to wild pig - as in just yards away - so there is no reason for taking long shots.
It is very important to be familiar with the anatomy of the pig vs. that of the deer, as they are different - essentially the kill zone is smaller on a pig and the lungs do not extend as far back. Do some research online and you will find diagrams and cross sections etc. to guide you. You may also check out a place online called "The Boar Blog" that has lots of great info.
Pigs are great fun to hunt, but it serves to remember that they can also be quite dangerous if wounded or cornered, so the pursuit deserves a good deal of care and respect.
In terms of eating, it seems pretty safe to assume that a dry sow or a boar up to a certain size makes for some FANTASTIC eating. Some folks say that any boar over 150 lbs or so is too rank and gamey to eat (unless you have it all smoked), and many times that can be true, but I think it also depends on various factors including what the boar has been eating. The 200 lb boar I just killed had been eating a lot of California Buckeye nuts and acorns and its meat is downright sweet, with just a hint of a ginger spice flavor!
Good luck and have fun out there in the swine fields.