So I've put 23 hours into this game and only beat the first three campaign missions, the first two solo/co-op missions, and the first two co-op only missions.
I've spent all my time perfecting certain of those missions, and I've managed to beat the first two solo/co-op missions without engaging a single guard, nabbing the gold ghost rating on Perfectionist. I've managed to get gold ghost on perfectionist on the first three campaign missions as well, but I've only been able to beat the second mission (Iraq) without knocking out guards. On the first mission (Benghazi), you have to attack the guards in both interrogation rooms, and the rooftops are damn near impossible if you don't take out two or three guards. On the third mission (Chicago), I'm nearly certain you can get both of the water pumps at the end without knocking out guards, but fucked if I can actually do it. Maybe if they didn't throw a time limit at you, I could.
Anyways, I've been having so much fun perfecting these runs, that I decided to fraps them and upload them to youtube as a guide or lets play or whatever. Pretty fun afternoon figuring out how to record, edit, and upload videos when i've literally never done it before. I wish I could upload high-quality videos to youtube, but I had to compress the shit out of them to get the upload time below several hours, and youtube compressed them further, so bleh. Either way, here's the first 4E mission, if anyone's interested:
http://www.youtube.com/watch?v=92W9Yy2xyRg