It's somewhat hard to tell due to the low framerate of the recording. However, there are several things that are very suspicious. In the beginning, when he's headshotting everyone, there's this very subtle back and forth twitch when he passes over his target. This is a classic indicator of an aimbot. Secondly, he seems to be staring at walls in areas that, for someone that claims to be awesome at the game, should know there's not going to be anyone there. This is especially true at ~1:28 in the video.
I've played valve and source games since CS beta, and I've seen a lot of hax. Everything from the uber noob ones where the guy constantly spins around in a 360* circle. To ones that only will lock on with a very narrow field of view. As I mentioned before, the subtle side to side twitch is usually a dead give away.
And those of you who claim he was sweeping and firing, he wasn't. He knew where the targets were before he'd step out of cover. Indicative of a wall hack.
I used to work with this kid that was part of the OGC clan in CS. And he showed me the hax that his clan uses. These hax are very sophisticated. You can toggle them on and off at will. It can cycle targets and turn the lock on feature on and off. You can change the field of view down to 3* or have it all the way at 360*. You can tell it where to aim, crotch, neck, head, etc. Make it autofire, can see through smoke, doors and other objects. It would also show who's where, on the other team, what weapon they were using, how much ammo in their clip, their health and armor status and how far away from you they are. It could also put a red line where the enemies barrel was pointing and so on.
Someone that's not a noob or an idiot could easily set it to make it look like they're not cheating. However, I'm pretty good at spotting them. I've been an admin on many a CS/CSS server.
This guy I can't condemn without actually watching him play. The video has too much lag, and TF2 has a strange lag also that makes you have to lead your target more than you'd expect, not to mention it has late hit registry.