Hey guys, i don't post here very often but i pretty much have been passing by here on a daily basis since my account was created, but usually just like to read and browse the site (Which is great btw)
Anyways i think i can answer this question, on the Left4dead 2 blog you'll notice the...
I can imagine him being pissed off that his neighbours house was being robbed in broad daylight, and to him nothing appeared to really be being done about it, but yeh on the other hand, he was warmongering from the start.
It's the one from the Soldier video if you remember, when the Heavy goes, "TO THE LEFT!", and the soldier fires at that medic and gibs him, then the sniper says something, then they all charge into the middle with the heavy shouting "GO GO GO!"
http://www.youtube.com/watch?v=QbZOeGyd61E
I just got it in the post today, although reading the news some UK Stores released it yesterday as a promotional thing, looking forward to going home and playing it!
Not the one's i've seen havent, sure the actual movement of the Heavy is still the same but they glide faster, easy to spot. I've killed many spies disguised as heavy because it's blatently obvious.