Not whining. Not raging. Just explaining why some community members feel betrayed. We are not made of money. I've played the heck out of L4D mostly because I thought I was just starting on a long adventure that was worth getting financially and emotionally and time(ly) invested in. Now, I see that my investment is being used to sell me another game < 1 year after I bought the first. How many Valve games only have 1 year of play in them? Its not that we don't think we got our monies worth, its that we honestly expected more. Maybe that is our fault? Maybe. But will we make the same mistake twice? I feel made a fool of and while I think L4D was a great experience that I am glad I paid for, I do not think that I was expecting to pay another $50 for 5 more maps one year later. I sort of expected new campaigns right away and to continue for years to come from my initial $50 investment. Maybe that's my fault, but the amount of gameplay I got from HL1+mods and HL2+mods and TF2 made me think L4D was the next big supported platform. Now, its consolized for the consumption of packaged gameplay. Not the Valve model that I signed up for.
Now ask me if I am ok with buying a map pack with 5 new campaigns and new weapons and game play and enemies and I might say "OK, I'll support further development on that great game I already paid for." But calling it L4D2 makes my first purchase seem worthless. I don't think people are pissed about paying for content, its more that this is not what we expected from Valve and it shows a lack of respect for the commitment they made to the L4D community.
I agree that its a good value and that the changes they have made merit a new title. Its just the feeling that they have abandoned L4D1 which no one thought would ever happen.