I loved this movie, too.
The Half-Life 2 feel is a great (and hilarious) point... I'm pretty sure it has more to do with the cinematography, though. Did you notice how the two major action sequences were all done in (mostly) one shot? Watch this video
here for some info on them, it's pretty impressive. It really drew you in... and I see how that makes it feel similar to what you'd get out of a first-person shooter.
And a burning car coming down a hill, blocking your path as you get ambushed? That's a definitely a page out of HL2.