Hm really? I think AF is more useful. I can live without IS on my lenses but i dont wanna trade AF. Useable high ISO might be the best i think. Way more than IS.
You talkin' to me Willis?
Yes, really. I did say "one of". I did not use the word "best" and I did not use the word "useful". No wonder so many arguments get started, when you paraphrase someone and change the meaning, then disagree with your paraphrased version you have committed a logical fallacy called a "straw man" argument.
I'm just havin' some fun...
I agree that the other two you state are also in that same category. An exact rank ordering of what is best, second best, etc. would involve a lot of factors including personal preference so best to avoid trying to do that.
AF has been around since the late 70s so whether we lump that in with other so-called "modern advances" is a choice. But sure, if I had to choose of course I'd take AF over IS.
High ISO capability is great, but distill it down a little further... being able to change ISO from shot to shot is even more useful/beneficial/wonderful/magical. In film days, there were different ISO films... but once you put a roll in, you shot at that ISO until you were done (do I have that right, I never shot film). Or imagine going out shooting for a day, planning to shoot say 5 rolls of film, but not sure what ISO you'd be using... man, you'd have to take along 5 rolls of film of each ISO you thought you might use. Yikes!