I disagree with everything except the characters being boring, which is fine as you can play as the first in L4D2 now.
The game was never really horror, so the light/dark mix doesn't bother me and I like the day parts. The spitter is incredibly useful, I much prefer the way the levels aren't just camp in this corner till things stop running at you then move on. The spitter makes it so you can't just huddle together in a corner unable to get hit by anything, also for she's vital for scavenge where you can explode dropped barrels and deny access to the generator for a bit.
The scavenge mode is and was much needed, the vs in the L4D1 takes way too long to complete a game, so to play as the zombies you needed to put aside about an hour to have a full game, with scavenge it's a lot less and you can just have a quick game if you feel like nomming some survivors.
Chargers/jockeys are good when there is cliffsides, and the difference between them and hunters is to spread out the pack like the spitter. L4D1 was too focused on huddling together and being invincible, the new specials all spread the pack out making it much harder when you get attacked by an organised zombie team that pull you all off to different directions.
With the original levels all coming over to L4D2 at some point, I really don't see me ever playing the first one again as I much prefer what they've done with 2.