Yep we all have our own experiences, and I can only comment on mine, AF definitely hits the iris and not eyelash, eyebrow or whatever.
To be fair you've picked out the worst review from Amazon regarding AF, there's plenty of positive ones and far more than the negative ones across the big bad web. The biggest complaint I see is with CAs, which is not something that bothers me a deal as it can easily be corrected, and I don't tend to shoot a lot in environments that tend to promote it.
Like always though we make our choices and pay our money. As I've mentioned before if I was doing pro work I'm not sure I'd trust any third party lens, but so far my Samyang has been spot on for my uses