Map Pack: "Prototype" [WIP]
Ok...just ran the map. Didn't finish it this time because I found something rather serious.
Aside from the fact that turrets and cameras can push buttons, the weighted storage cube spawns out upon load.
Just try it. Quick save as soon as the cube is dropped. Then quick load. It'll be there for half a second or so, then it'll just vanish. Poof.
Ooh.
So my fix for two boxes when loaded didn't work. Dang.
Yep, same problem here. The cube disappears on loading.
Other things i noticed:
The wall that moves to reveal the turrets is concrete, but not portalable. Consider changing the texture, or make it portalable.
You still need func_portal_bumpers in places where metal meets concrete.
The glass in the first room can be broken (eventually) with the gravity gun. This is no big deal though, as although it makes the first part easier, it takes a while to do.
I like the fact you have added light strips to the first room, but you need to add overlays to them to give a more even lighting effect. This can be annoying to do properly though, so maybe leave them for now, at least until you have sorted the major bugs out.
I will play through this map again properly when you have fixed the cube spawning bug, as it's anoying to drop the cube in the water and have to restart the entire map.
Okay, everything fixed. I'm thinking this is pretty much the final release, once I find a way for the tube to suck the player up and move them down it, and put in a few more portal bumpers. So yes, nocturnalGhost, you can playtest it now. 
The map is coming along nicely. I'm glad to hear you are close to completion. However, I have a few more things you may need to look at. (I bet you hate me by now. ) 
The broken button has no visible effect when stood on to show that it is broken, which may confuse people.
If you put the box on the any of the buttons whilst also standing on it, then get off, the button unpresses, even though the box is still on it.
The doors still have a small gap on one side, that can be seen through when closed.
If you stand on the button that makes the steps rise, whilst the glass still exists, it shows the zig-zag effect where the step edges touch the glass. Consider making the glass slightly thinner on the outside.
Inside the room with the rising steps, there is a wall with the nodraw texture, on the face directly above the door.
It is also still possible to get stuck in this room on the opposite side of the glass, unable to activate the steps (although it takes some stupidity to do it). The way I see it, only the bottom half of the room needs to be concrete, which would make it impossible to get in the room until you break the glass.
Other than these few things, the map is looking a lot better now. As for your problem with getting the player into the pipe, try using a func_push pointed upwards, then another pointing into the tube at the top. The upwards func_push will be activated when the player jumps whilst below the pipe. (I like the effect you used there btw )
You may also need a point_clientcommand to make the player crouch whilst in the vent as well. Use the command "+duck" when entering the tube, and don't forget a "-duck" at the end, so the player isn't stuck permanently crouched afterwards.
*Edit: Corrected commands for crouch.
The broken button has no visible effect when stood on to show that it is broken, which may confuse people.
If you put the box on the any of the buttons whilst also standing on it, then get off, the button unpresses, even though the box is still on it.
The doors still have a small gap on one side, that can be seen through when closed.
If you stand on the button that makes the steps rise, whilst the glass still exists, it shows the zig-zag effect where the step edges touch the glass. Consider making the glass slightly thinner on the outside.
Inside the room with the rising steps, there is a wall with the nodraw texture, on the face directly above the door.
It is also still possible to get stuck in this room on the opposite side of the glass, unable to activate the steps (although it takes some stupidity to do it). The way I see it, only the bottom half of the room needs to be concrete, which would make it impossible to get in the room until you break the glass.
Other than these few things, the map is looking a lot better now. As for your problem with getting the player into the pipe, try using a func_push pointed upwards, then another pointing into the tube at the top. The upwards func_push will be activated when the player jumps whilst below the pipe. (I like the effect you used there btw )
You may also need a point_clientcommand to make the player crouch whilst in the vent as well. Use the command "+crouch" when entering the tube, and don't forget a "-crouch" at the end, so the player isn't stuck permanently crouched afterwards.
Why would I hate you? This map would be even more frustrating if there weren't people like you to test it. Thank you.
One last thing: I added the blood splatters and bullet holes to tell the story of an employee who attempted to escape after the disaster and died trying to get out of the turret room (much like the hidden rooms filled with "the cake is a lie" scrawlings) in the original game. Did I succeed?
Yes, I think you did very well with that. I noticed it the last time I played through, but forgot to comment on it due to focusing on the cube respawn problem.
Also, I made a small error in my suggestion for the tube in my last post. The command i suggested should be "+duck" and "-duck", not "+crouch" and "-crouch".
Okay, this is the final build. This was the first map I ever made, and I'm really happy with how this turned out. I added some eye candy to the end as a reward for the dilligent player. Enjoy!
Okay, I lied. Map2 isn't finished. However, the next part of the level is a somewhat simple puzzle and some eye candy as a reward. Tell me if you like the new effects at the end. (I added portals there so you can skip the puzzle.)
Also, you can shoot portals through the tube pieces.
The final room, I got the two cubes to the button with a fair ammount of ease. However, they don't activate the button. You need to stand on it. And even then, the button doesn't do anything.
Something strange though: When I was at the part with the turret, and the breaking into the glass room: If I was standing on the side of the portal that the room was on, and the turret fired, as soon as it hit it's side of the portal, the missle would evaporate, as if it went through a fizzler. However, if I was standing on the side of the turret, it could go through the portal just fine. Most perplexing.