Pros:

Feels a lot like team fortress
Plays like a l4d game
The concept is really nice and original
fairly long for being one map (took us 30 minutes)
The cart having weapons and the like on it was a nice touch
The tooltip forthe alarm was chuckle worthy

Cons:

From the time you have to turn the alarms off to the end, it becomes a battle
The cans being so far away sometimes gets us split up then destroyed
The last few cans took a few to figure out how to get
Anyone who hasn't played much team fortress would probably jump into that hole at the end.

Conclusion:

This map is great for a team who doesn't have a whole lot of time to play, but want to.  It's a wonderful throwback to team fortress without making the map just a "point a to point b" map.  Even on the lower levels it's still a challenge and still extremely fun to play.  At one point we found chompski and had him ride the cart.  Him and one of our teammates rode to their deaths, it was quite funny.

*Edit*  Just played it again, never knew there was a checkpoint where you have to pull the lever.  LOVED that, saved us a lot of frustration!

Pros:

-A very polished campaign, one of the best I've seen in a while.

-While I have not personally beaten Half-Life, (which is on my list of things to do)  I do see the amazing attention to details within the campaign

-The soundtrack that we heard on there was superb, if it's from halflife I do need to get it

-Was overall a very clean polished campaign, it carried over well for the L4D 2 installment

Cons:

-We restarted twice on the first Crescendo, once when we didn't know where to go, and another because a tank spawned during the crescendo.  Now I know if I played Half-Life, I probably would have known where to go, but none of the group had.

-The fire lvl gave me some issues with Glare from the lighting, it was also hard to see through all the smoke.  We did get through it fairly easily, it was just a small nuisance that I had with that particular part.

-We had to restart the finale because we didn't know where to go to escape, isn't too big of a deal either really.

-The Tank premature died in the finale while we were up top.  I'm not exactly sure why, but I usually record our playthrough and if you're curious I can possibly get that to you.

-The tank knocked me into that little groove off the the side of the train, Running all the way to the end while fighting zombies can prove to be Brutal, but it wasn't too difficult, we just used a bile and ran for it.

Conclusion:

Quick note: My review is based on what the group as a whole thought about the campaign.  I just took the appoximate average.

This campaign is a wonderful addition to a growing collection of addons.  It perfectly replicates much of the Half-Life saga and it even gave me a scare or two.  I'm looking at you, bodies that drop from the ceiling!

The music that was added in was superb and was just fun to fight the finale to, it broke up the monotony of the regular Horde music.

The maps were immersive and fun to play.  The whole campaign took us 3 hours, But I'd say it more took us about 1 1/2 to 2 hours.  We had a guy on board who didn't have anything downloaded, and never knew how to make custom maps work.

If you enjoyed half life, you're going to love this map.  Thank you for the work that you invested in it, it really shows.

Pros:

- Custom voice was a great addition and added to why the survivors were there
-The custom tank skin was adorible, I knew about it, but a teammate didn't and when she saw it she squeeled into the mic.
-The enviroment was very creative.  I especially enjoyed the custom snow and fire.
-Speaking of custom, all the custom additions were very very nice.  It was a relief to be away from the deep south and in a new territory.
-The campaign was kept engaging, going from Ice to Fire, but also able to tie that in with the story.
-Seeing the level one way then going back, very Hard Rain-esq, it was very interesting to see.

Cons:

-It was very hard to see at one point.  The glare from the fire made it difficult.  I believe it was the most annoying where the barracde is located.  Almost all of my teammates complained about the glare.  In fact, talking to them now, it seems to be the biggest complaint.
-The map with the metal detector, I think that's the second level.  We didn't know if the infected would ever stop coming, we spent a good 5 minutes in the saferoom shooting infected through the door, we then spent a while trying to figure out where to go, it wasn't too difficult, but teamates were falling all over the place, we did it on normal, but it would seem anything above that would begin to get difficult.
-There is a pretty big glitch spot that we found for the finale,  across from the chopper there is those walkways with I believe an ak, we stood there and nothing touched us.  The Tanks would spawn up and die immediatly.  Thankfully, I usually record me and the group going through levels, so if I'm being a little unclear or you want to see what we specifically did, I can get that to you.

Conclusion:

First of all, I basically registered to review this map.  I had a group of 3 others with me and we all enjoyed your campaign.

The voice was done very nicely, thankfully you placed it where everything was relatively quiet and we could all hear what it was saying, the first one on the way back most of the team didn't hear it however.  It was the one where he was talking about the fire alarm going off or some such.

I have a very low end computer (6150 Nivida Graphics! D:)  and Even with such a terrible card, I could play relativly well even with all the fire and "noise" going on in the fire levels, but one can't really fault the map for a computer that doesn't even meet the minimum requirements for the game it's running.

All in all, me and the group really enjoyed this campaign, you can tell that a lot of thought, time and effort was put into it.  But you can also tell that it can be improved.  The biggest complaint is the horrible glare from I presume is the fire, it was really distracting.  All the custom content was just icing on the cake to a wonderful campaign.