just my opinion, based on my observations and reasoning
The one person I know personally that used a .223 on a deer (Ruger Ranch Rifle) was shooting a blacktail buck in the Pacific NW ..... he has nothing nice to say about the round.
Properly loaded, out of a long barrel, with the right twist, .223 would be adequate for short range, and small deer.
Having done most of my hunting where wide open spaces are the norm, and the deer have all the food they can eat pretty much year round .... I think there are better tools for the job.
Having seen quite a few deer running around with wounds in the days after opening weekend, or dead and not recovered, I think hunters should really use the best tools they can get their hands on......
TheGolden Rule of Tool Use: "If you don't know what you are doing, DON'T."