Enebias: I recently completed Downfall, and I can say this: it was one of the most disturbing games I ever played. Downright psychotic! This words, coming from a not-easily-impressionable person like me, are to be taken as a true compliment.
I will not enter in details, as even a minor example can be a HUGE spoiler, but if you want to have a nice trip into total madness, this is definitely the game for you!
It is a really well executed point and click adventure with an intriguing story; most puzzles are not complex, but their relative simplicity woks wonderfully with the flow of the story, allowing the player to immerse him/herself in one of the darkest setting you can find in a videogame.
My only complaint stays on the bug side: during the entire playtrough I noticed a few of them, especially a particularly annoying one that prevented me to use inventory objects until I pressed the "scroll" arrows on either side of the bar. Nothing game-breaking, though. I warmly recommend it to a mature audience!