Mike,
I can offer some very specific insight to your question:
My dad and I began reloading our own ammunition almost 20 years ago. In that time, dad's gun has not had any other bullet through it, just that exact Hornady 100gr pill. It has accounted for ~30 deer, the majority of which expired within sight of where they were first shot. It is that bullet which has me convinced that, in the hands of a truly good rifleman, the .243Winchester is 100% adequate for taking thin-skinned, medium-sized game.
However, back in about '98, Dad came out to California and we went on a wild boar hunt. I took my .270 and, despite my reservations (and the guide's!) dad pulled his .243 out of the gun case, instead of my old 7.7 Jap. I can't really blame him, seeing how ugly that Arisaka is, compared to his 700 BDL, but it turned out to be a bad decision.
The guide took us around a little side-hill and there, about 200 yards ahead and above us, was a nice old boar. Dad took a steady rest and the guide put his binoculars on the hog. At the crack of the shot, the guide saw dust fly right on the point of the shoulder and yelled, "good hit!", but that was the beginning of a long, frustrating afternoon. We spent about an hour searching before the guide went back for his dogs. After another 2.5 hours, he reached the conclusion that the bullet must have hit the sheaf of cartilage on that boar's shoulder because if there had been any kind of blood trail, those dogs would have found it.
The next day, the guide spotted a band of pigs moving across a small canyon and positioned dad just off the edge of the trail they were following, maybe 30 yards from where it came up out of the canyon. The guide told dad to shoot the 2nd hog through, which turned out to be a 125lb boar. The 100gr Hornady hit just above the hog's left eye and, needless to say, was more than sufficient, at that range and with that placement!
I know it's just 2 shots and that, with hogs especially, the size of the critter and bullet placement are so crucial, but what I concluded from that hunting trip is that the .243 is not an ideal cartridge for hunting hogs, although if the range is short and the hog's not too big, it can be pressed into action. Dad went out and bought a Savage 110 in 7RM, hates the recoil on it, but has used it to good effect on two cow elk hunts. So, he knew a bigger gun was in order, but he hasn't been hog hunting since!
Although, if you want to extend an invitation, I would very much like to give him a hog hunt for Christmas! Say the word and we'll pack our bags and head south...but not with the .243!
