The AI is terrible. I got through my stealth run by doing the silent run or invisibility. Even without those, there would be times when Mike would take a guy out feet away from the enemy, but because their back was turned, it didn't matter. The only nice thing about the AI is that if an enemy spots you, the alarm won't go off like crazy. They physically need to run to the alarm panel and signal others. Even that has been done far better in stealth games from a decade ago, like, think shooting out pocket radios in MGS2.
I only played the Peace Walker demo and the AI was there. But to be fair, the AI in Alpha Protocol is probably better than the AI in the Splinter Cell Conviction demo.
In my shooting run now, using the assault rifle is surprisingly not that bad. It's better than ME1 combat, at least, and gets better as I upgrade. I'm also surprised by how different the game is playing as a raging asshole. Like, at one point I pissed off an arms dealer and when I was going to assault a location, the people guarding it were now heavily armed soldiers. In my previous run they were just regular security dudes and I was able to get past them by shooting the shit. Here, I just resorted to shooting him in the face because he was all about checking my credentials.