Anyone who is on the forum in a somewhat regular basis should know better than to listen to fish (aka, the troller). He obviously has an agenda with his hatred for Dodge/RAM/FCA, and a love affair with his blue koolaid.
To the OP, the vast majority of reviews I have seen on the 6.4 have been positive. I have a friend that was a fan of another brand for life, and bought a 6.4 two years ago. Short version of that story is his truck was just totaled in an accident (no injuries), and he will be replacing it with another 6.4.