Team Fortress 2's long awaited Mann vs. Machine update launched yesterday and so far it's been a mixed bag. As Mike Fahey mentioned earlier today, matchmaking is an unplayable mess, due to the sheer demand and a lack of community servers. Hopefully that will be resolved in the coming days, but in the meantime you can still play the mode directly, using the server list.
And that's exactly what I did!
The video above is from the last wave of a match I played earlier today. As you can see, they've significantly revamped the system to include perks. Near the end, my Engineer's turret was a monster.
Oh, and a word of advice: Beware those sentry busters. They pack a wallop.
P.S. I am aware that I suck.
P.P.S. In retrospect, Engineer was a poor choice for video.