The loss of several gameplay options from previous games and the overall watering down of the stealth elements is something I would ordinarily frown upon, especially given my love of such a great franchise.
But Ubisoft did something fantastic. They didn't just change the game because "it was time to do something new". This all ties into the story, and the story all funnels into Sam Fisher's character. My experience is somewhat limited, but Conviction's Sam may be the most realistic video game character I've had the privilege of controlling. You already have Ironside's fantastic pipes behind him, but Ubisoft crafted a compelling and intimate story for Sam along with some really stunning and believable body language. When you combine that with great pacing, a still-strong emphasis on stealth, more forgiving gunplay mechanics, and a storytelling methodology that blurs the lines between gameplay, cutscenes, and quicktime events, you get this.