* Atmosphere and setting are done with outright astonishing attention to detail; second to none. Going into the quarantined apartments actually had me freaked out (particularly so soon after the car chase panic event); that's never happened to me before. The elevated train is absolutely beautiful. The underground tunnels give me shivers just thinking about them. Wonderfully done.
* Supplies layout is just fine - no major issues one way or the other.
* Some of the most creative panic and crescendo events I've ever seen, and the lead-in to the finale is very impressive.
* Implementing a Scavenge finale in L4D1 takes some real creativity, and this is to be applauded... despite the setbacks therein.
* Ostensibly there's a Tank in the nightclub, but I've never actually seen him or had to fight him. I count this among my blessings as I utterly loathe tank+horde events, but this is definitely a bug.
* Progress after the nightclub is a bit awkward. Took a while to realize that the boarded-up doors were the way to go, and took even longer to get those boards out of the way.
* The individual maps are a tad long by themselves. I'd suggest rearranging saferooms so as to make it into a five-map campaign, rather than four.
* I'm not a big fan of crawling through vents and the oh-the-vent-just-fell-apart cliche, but, meh, that's just me. Well implemented, though!
Finally... the finale. Oh dear G-d almighty, the finale. This deserves a Cons section all its own:
* No gas can counter, so you don't know how far you've progressed. This is, however, probably unavoidable. :(
* There's already a horde equivalent of infected present when you first show up in the area, and hordes continuously respawn with zero "periods of calm" (which you normally see in Scavenge finales in L4D2) unless and until a Tank shows up.
* Speaking of, those Tanks are ridiculously easy in this map because of all the open space - indeed, when you hear a Tank, it's blessed relief, because that's when it's calm enough for you to get cans transported. One should never be *relieved* and *grateful* to hear a Tank coming!
* The gas cans are placed much, MUCH too far away (and only one at a time each time).
* Worse - far worse - you can't gather 'em in stages (grab one, toss it closer, grab another, toss it closer, repeat until able to fill things up) as they'll ultimately vanish and respawn, so you have to run alllllll the way there and alllllll the way back for Every. Single. Can. GRARGH.
* The windows leading to the gas can in the apartment are too small - it's way too easy to become trapped in there.
* It's surprisingly easy to sometimes miss the fuel door and thereby end up accidentally tossing cans into the trunk of the car - where they're impossible to retrieve.
* In Single Player mode, things get much, much worse...
--- Bots can't retrieve gas cans or throw explosives - so crowd control is strictly the domain of the player, and you have to toss away your hard-earned gas can to do it, which can easily cost you that can due to either accidental stray fire or vanish-and-respawn.
--- Botnav isn't sufficient for them to follow you closely enough to cover you as you retrieve cans. (To be fair, I'm not sure this is something the map designer can actually fix, only compensate for.)
--- "Calm" periods with the Tank present - where human players can just keep dodging the Tank with all that space to work with and retrieve cans - are worthless with bots, because they (normally quite sensibly) try to take the Tank down as quickly as possible.
* And all of these issues come well before the incredibly frustrating gas pump explosions that occur seemingly at random and completely end any attempts right then and there. (Tho, to be fair, I understand that those will be patched in a future version)
Rearrange the maps a bit so the first three maps become the first four, and rebalance the finale, and this becomes arguably the greatest campaign L4D1 has ever seen. But as it is, the long maps make it a tad problematic and the finale - while showing a tremendous amount of promise - proves ultimately to be freakishly unbalanced. I have very high hopes for the L4D2 version of this campaign.