I had an uncle that began hunting with the .243 about 1962 or so. He averaged a well hit deer lost about every three years or so with the cartridge. Bullets have improved greatly since those days, and I don't hear of the .243 failing , on average, than any other cartridge.
My thoughts on the .243 as a hunter? Works, but I follow these rules:
1. 100 grain or heavier bullets
2. 200 yards max range.
3. Standard bullets are ok for the 125 to 140 pound whitetails around here.
4. Premium bullets for whitetail at 200 pounds or over.
5. Practice enough to hit your mark every time!