The game is optimized pretty well. Definitely nowhere near as bad as GTA IV was.
Theres a built-in benchmark option as well. Maxed out settings with AA on (no value option, just ON or OFF) and PhysX at MEDIUM gave me 50fps average at 1680x1050. Game runs really well. Smooth performance throughout
The combat is fantastic. Animations are really good. Behind cover when you're getting shot at, the facial and body animations kinda reminded me of Uncharted. They're not in one static position. The PhysX effects are really cool. The cloth movement adds a nice realistic touch to the overall presentation. The particl/smoke effects are quite noticeable as well. I personally love the lighting engine in the game. Highly polished game. Character models are very detailed, even more so in cut-scenes and voice acting is top notch. Car handling takes a little getting used to on Simulation mode. You are given 10mins to roam in the open world before getting to the objective mark. And yes, the magazine covers scattered about are 18+ so please play this game alone.
Very pleased with the demo overall. Can't wait for the final game. Will be posting screenshots soon.
Screenshots