Left 4 Dead has been a very successful franchise, and there was a lot of controversy over the quickly released sequel. Many complained that the maps and new enemy types did not qualify for more than what should have been a DLC pack.  My complaints with the franchise, however began when a friend talked me into playing the first L4D. 

My friend who was very excited to show me this fantastic co-op game was quite crestfallen when I said I was not satisfied with my purchase.  Maybe the problem is that I had played TF2 first.  As we were progressing through the level I noticed that while we had a choice of how we wanted to look, there was no determinable difference between any of the players.  I could choose between young professional and war vet, but they both have the exact same abilities.  It would have been much cooler if each filled a role.  This would create a better team dynamic and given me an incentive to replay the maps, this time as a different character.  Also I don't like AI partners.  I did not realize this was driving me crazy until I played Boarderlands.  I am not always able to play with four friends and I despise playing with strangers.  Borderlands elegantly scales the difficulty and reward based on how many players are logged in.

If Valve is indeed planning a L4D3 I would hope they bring over some of the TF2 team and get some classed based scaling MP in there then, and only then,  will I sit up and take notice.