Yes cheater... I put on timescale 0.01 and its clear. He first aims manually to a area where he can see the enemy, then he clicks the autoaim once without holding it, so the aim goes right on top of the target, but it seems natural at normal speed because he doesn't keep the autoaim toggled. He just clicks it once or twice, so the aim goes to the spot, as a help.
Watch the first couple of minutes with timescale 0.01 and see that it's impossible for a human to move the mouse so quick and put the aim right exactly on the person. The aim stays there for a while then when he unclicks it wanders away, giving the impression, at normal speed, it's natural aiming. The first 2 kills of the 1st demo it's reasonably noticeable, and when he is under the garage and he kills two guys very far away with perfect aim then there's no doubts.
@natirips well in UT you can never be idle :p if nothing else there are always weaps and shields to pickup