I have played the game with my friend at his house, IT IS ****ING AWESOME! I can see why valve made it a sequel, there was some stuff they couldn't add to the first game, like the new infected, the melee weapons, the new fun stories and modes (I still like versus mode, NEW INFECTED FTW), and the different types of special bullets.
One of the funniest things we did at my friend's house was a certain achievement mission in dark carnival involving a certain lawn ornament and protecting it, I was using it as a melee weapon and I got more kills than my friend, who had an axe and a machine gun with flame rounds. My ass litteraly fell off from laughing, I should be getting the hospital bill next week.