I'm playing on the PC, but using a 360 controller. Agreed on the voice comments, getting rid of Michael Ironside was a huge mistake. Fisher used to have an iconic voice. Now, in this game, I watch a five minute cutscene of a bunch of operatives, and I can't even tell which one Fisher is supposed to be because nobody stands out from anybody else. I'm not a fan of Grimsdottir's new voice actress either.
I haven't gotten far enough in the game to know if I'm going to like the main gameplay more, (obviously we all know the game hasn't been as good since Chaos Theory), but there are already some major annoyances. First of all, what the hell was wrong with one button for non-lethal and another for lethal? Now, you hold a direction on the d-pad, wait for the menu to pop up, and press X to toggle between the two.
Secondly, I'm not really a fan of the way that they tried to remove most menus from the game by making you walk around and talk to people on your plane to accomplish the same thing. More immersive? Maybe... but it's like they took the most annoying parts of Mass Effect and shoved them in here.
Finally, I really hate the 'press B to enter cover, and then press A to jump to other cover' mechanic that they introduced I think in Conviction that continues here. The best parts of the Splinter Cell series involve the tension of slowly sneaking somewhere to avoid detection when you know you don't have much time before someone comes down the hallway. I actually don't hate the mark & execute mechanic, and I definitely enjoy that Sam has been made more powerful for when plans go to crap... but things like this cover mechanic are trying to shoe in unnecessary features to try and sell to the CoD type crowds.
Haven't tried any coop or Spies vs Mercs yet. I loved coop Splinter Cell back when college friends and I used to play it in split-screen, but haven't ever really gotten much into it over Live.