Sorry fuzzy, ^Dread beat you by 30 mins in posting this to me.
Impressive, impressive how fast they do it and impressive how bug ridden halflife2 appearantly is.
The jumps he does are not normally possible, notice how he appears to levitate when jumping from roof to roof. Dread said it was just like glitchy quake physics.
I don't think they used a "stock" halflife to achieve this, though.