I've beaten all the mainline SC games. Conviction is Splinter Cell for dummies. No wonder Sam Fisher is so pissed in this game. It takes all the complexity and depth away from what used to be a challenging stealth-action series, converting it instead into action-stealth.
Surprisingly, regardless of this obvious catering to the lowest common gamer, Conviction manages to be entertaining despite this transgression. This is mostly due to the Mark & Execute system, as well as the Last Known Position system. (However, having the screen go all black and white while in the shadows was a retarded idea, because that means most of the game is played in boring black and white.) Conviction's plot is retconned trash, and the less said about it the better.
Basically if you're looking for a brief and easy action-stealth game, Conviction will do you fine. But if you're looking for a great Splinter Cell game, check out either Chaos Theory or Blacklist instead. Conviction was ultimately a confliction. You can't always please everybody Ubisoft.