I just beat it with AI's
The first time we all got killed, second time i tried to hop off the bridge and back to the lower ground to get to the generator fast but realized they wouldn't let me do that and instead they made me hang from the ledge, thus ending the game even though the others could've helped me back up fast, the third time i didn't do that, i went down the way i came up and i died in success
I should've played as Bill... also, the survivors are lacking voices in Left 4 Dead 2, Francis always says "What the hell is this" when he sees a bile jar, incendiary ammo, or something, he doesn't say "Pills here!", "Adrenaline here!", "Pipe bomb here!", "Molotov here!" (although he does say "Fire." when picking up a Molotov), nothing, why must Valve be so lazy! :(
