I finished it with 29 hours play on Tuesday. Only missed the Cloak & Dagger mission.
To get the 4 different endings in 1 fell swoop make sure you talk to Taggart and Sarif on the last sections of the game. Taggarts location is off the outdoor walkways after you speak to the guy with the beard in the control room. Instead of following the marker he is on the second level down off to the left.
You get a call for help from Sarif as you see the walkway blocked by some boxes you jump over. If you jump over them and havnt spoke to taggart you cant get back, so make sure you do that first. Then once you jump over the boxes there is an elevator, use that and Sarif is in that area, behind some crates that are blocking a doorway.
Then after taking out the boss walk into the control room and save after you get the speech and the buttons open up. Left side is Sarifs recommendation, right side is Taggarts, middle is about you and the door to the left is the final one. So you can watch one then load and watch the next and so on. Dont forget to watch right through the end credits to get the D Project achievement and a small sequence which ties into the first game in the series.
Definately been my favourite game this year, would love it if they remade the first one using HR game engine and mechanics, would work so well.