Apparently, some time in between L4D1 and L4D2, I ran over the AI directors dog or something, because he decided to be a total asshole. I've seen 3 or 4 Special Infected straight up spawn out of thin air, the AID doubling up on spawns in the same room and multiple times wherein it spawns a tank during the Dead Center mall crescendo.

The level design is really superb. Apart from the fact that the maps are much more dynamic and actually tell a story by their progression, Valve obviously had Versus on the brain when designing them this time around. A lot more hazards, ledges, and alternate routes to split up the Survivors and give the Infected opportunities for big damage or even instant kills. It's a whole new game. I've only really had time to dig into a solo campaign (I did the last two acts of Dark Carnival in a CO-OP campaign and Swamp Fever in VS mode) for an hour and a half, mostly dying repeatedly on part 3 of Dead Center on Expert. What I've noticed most about the level design is that they've carefully removed almost all the campable [sic] tight corners with clear lines-of-sight to all incoming zombies. On the outdoor levels in the demo (Parish), this was mostly done by replacing many walls with fences and low-rises that zombies can climb over or whack through. In the indoor levels in Dead Center, they've obstructed the space ahead of the corners with junk like shelves, and introduced more complicated vertical layouts. The common zombies also weave erratically now, so they're hard to clean out by firing repeatedly at the same spot and they will flank you. It's really this kind of thing, and not just the new special infected, that makes it considerably tougher than the first one (to someone who knows all the old tricks -- it's about equally hard to a beginner).

I like all the new weapons. They fill in the gaps left between the niches carved out by the old L4D weapons.

I also appreciate the subtle weapon balances. The MAC-10 is slightly more accurate and damaging than the old Uzi and you can hold more ammo (the lack of which made it chronically useless in the longer L4D maps). The pump's ammo has been sliced clean in half, but it also seems to do slightly more damage. The designers really paid attention to the subtlest balance issues of the first game and improved them where needed.

The only issue I have is that there's no reason to choose the standard pistol over a melee weapon in the easier skill levels. I suppose if you have a the riot or auto shotgun you might want something to pick stuff off from long range with.

On Expert though, one common infected's damage makes the risk/reward of using a melee weapon much higher. The melee weapons still have plenty of use though, since they have a ridiculous cone of effect. It feels like a swing covers your entire field of view. It becomes really evident on some parts where you're at a doorway/exit and can reliably cover it with weapon swings and push-backs while the rest of the group covers other parts/picks off specials. Personally, I feel if you need to conserve ammo, it's much more effective to pick zombies off at a distance with the dual pistols, though you may have to haggle with a teammate to give theirs up.

Now on the other hand you have the 50 cal desert eagle. You can only carry one and it only holds eight rounds at once, but goddamn that thing is awesome. The best part is: when you go down you are still a zombie killing machine. It kills Smokers in a single headshot. Also, the utility of the second tier sniper rifle is amazing. I favored the assault rifle in the first game, but since I was always shooting one round bursts, this is perfect.

On the subject of the new Special Infected, I've seen the potential the Charger has and it's absolutely brutal for Vs. mode. He doesn't do too much damage. Instead, how far away he is when he charges is about equivalent to how far a hunter needs to be for damage. He has the downsides of being easily sniped when coming in, and of always making noise (so he can't just run in and scratch as well). But on the other hand, once he's pinned a survivor he has to be shot off rather than melee attacked, and he gets damage on other survivors that he knocks back in addition to the one he pins.

He might not be as good overall as the Hunter since he's slightly more situational, but there will be times when he will just wreck the survivors (like when you get them all lined up in the gauntlet in Parish2). Regardless, the Charger is falling into the same sort of trap that the Smoker held in the first post-release. People see a lack of damage but ignore the insane amount of separation that occurs as a result of a charge (compounded by the fact that he knocks survivors around). Its a bit odd, since the charger seems to be a better bet at breaking up the survivors than the Jockey, who, while hilarious to play as, is taken down way more easily, even if he gets a mount.

I see the Jockey much more in the Smoker's position as the "weakest special." He's fairly fragile and easy to pick off once you've got mount; you've got to depend on all three other Survivors being busy, like the Smoker. He'll be nice to go in and lay down some regular melee, though, just because he's difficult to see.

Smoker did need the boost he got. Being able to grab Survivors through common infected was a vital addition, and the inability to insta-smack grabbed Survivors (even if the gap is only half a second or whatever) is welcome.

Spitter is all about area denial. She doesn't need much life because ideally the Survivors won't ever see her. The idea isn't so much to damage the Survivors (though if you get in a situation where you can, awesome) as to cut off escape routes and choke points to force them in positions more vulnerable to the other specials. Imagine for instance that the Survivors are sprinting through a narrow hallway. Spit at the end of the hallway so they can't get out, and now the Charger is clear for a good run.

It's a hell of a lot meatier than the first game. Where the first game felt like a very cool mod of a game (Counter Strike), this feels like an actually for-serious game game.