personally i think it makes it really biased when you're actually looking at him thinking he cheats before you even watch something because the tf2 demo system blows, so these are just my observations based on the 4:30 that i watched of the frag vid (because people normally don't put clips of them missing in frag reels :V)
from what i saw, it looked like he walls or something based off of the fact that he ran into the wall twice and scoped in or just stays paused staring at the wall at two points that i saw in the video (this could also be explained by him just waiting on comms or typing to someone on steam friends for a second or two lol)
http://www.youtube.com/watch?v=YhzAB26E-Gc#t=4m13s
the headshot attempt on the medic appearing from behind the crates at 4 minutes 15 seconds looks like either he has one of the fastest reaction times ever, he guessed that someone would appear at that moment and fired, or he could see through the crates and fired and that's basically when i stopped watching altogether :V
esentially i thought that he was just really good at killing scouts, and most of the first 2 minutes seems to be against the same scouts over and over again, but he plays against a lot of others as the movie progresses so i have no idea~
edit: my bottom-line is that i don't think he cheats, and judging people on their frag movies is dumb because you don't know the timespan of the videos or how consistent x person is or if the people they are playing against are any good