I just finished the first homicide mission and having fun. Still trying to understand how to play it. Little confused on question asking. I believe it does use the same engine in RDR. The trees and shrubery have the same look and physics when you walk through them.
I agree determining people's intentions can get difficult and it seems to be getting tougher as you move through the game. I'm on my 3rd or 4th homicide case and I still haven't found an easy way to determine between doubt and flat out lie. Right now I just usually review my clues and if there seems to be nothing I can use to accuse them of a lie, I go with doubt but lately, even the truth has been difficult to read correctly.
Personally I love the fact that it's not an easy read because I think that would make everything too easy. This way it's a bit more realistic IMO. I also really enjoy the banter between Cole and his partner while they ride to their next location. Some of the talk is really hilarious.
I've also noticed some excellent attention to detail as new cases will make references to prior cases already closed earlier in the game. I really think this helps keep everything tied together in the course of the game's timeline rather than just random cases with no connection to the game's world. The street crimes in free roam tend to be more irrelevant to the overall game.
So far I'm really enjoying the change of pace this game brings. I really curious to see what Magnum thinks considering his background.