I loved this this movie. Yes, it is dense in dialog, but I found it totally fascinating. At times I felt like I was in the room actually watching history take place. It's too bad some people have the attention span of a gnat and can't realize how important the events of this movie are.
The performances, direction, and cinematography are all top caliber. Like the best action movies, it made 2 1/2 hours fly by. I'll be totally surprised if there aren't multiple Oscar nominations.
I agree you really feel engaged in quite a few of the scenes as though you were actually there. This was definitely intentional to especially in any scene where Lincoln is telling a story. You the audience, just like all the politicians around him, are forced to listen to his random tales without interruption and you are just kind of left staring at that spectacle. It's amazing. Some of the lighting and scenes are so excellently done too.
When Lincoln hears the bell chiming to signal the end of the debate over the amendment and he walks toward the window curtain, being covered by the light. That scene left me so shocked. Then there is the scene at the end where he tells his butler that he must take his leave. Everyone watches him walk slowly down the hallway and we all knew he was no more.