[RELEASE]There and Back Again.
I had a feeling it was going to be stairs. Like I said I do plan on re-using the stairs (I was proud when I got them working lol). I plan on making a few prefabs for them and polishing them up. I may use Valve's solution but I have a few idea I'd like to try first.
you could probly also put a func_noportal_volume that you disable when the stairs are up? or just make it a func_brush or some such simliar thing that starts disabled and enables when the stairs are down. to prevent the player from putting a portal under the stairs. in THIS map it wouldn't really matter. but if you use these in future maps you might want to have the stairs up. but not have the player portal "under" them
In this map you couldn't put a portal under the stairs because texture under the stairs is a metal grate but that's a good thing to keep in mind. I think I lucked out on the design there cuz I never thought about putting a portal under the stairs. I plan on making prefabs based on those stairs, I like them.
well planning for the future is a good idea. especially if you plan on making prefabs out of them, but besides you need a small buffer on them if you want it to be perfect (so that you can't see the part where each stair entity meets)
I'm not quite aiming for perfect, just yet. 
I've been playing around with the stairs in a "test" map. I've manged to reduce the lines from the stairs. I believe their coming from the bottom edges of the steps. I moved the grating up and then it drew fewer lines and they were thinner. I think I got could make something work with an "invisible" textured brush but I'm too tired to try it tonight.
So I see you've already gotten a lot of technical tips, which are a bit beyond me (I haven't tried my hand at map construction yet) but I wanted to be the first here to give you some really solid praise on this map from an aesthetic standpoint. I think you did a really great job of creating an entirely alternate but beautiful look to the lighting and architecture. It's not Aperture standard by any means; it's kind of a mean, gothic industrial look. And personally, I thought that the looming black ceilings helped with that a lot - it makes the rooms seem like they disappear off into infinity. When I first walked through the map and saw the colored lighting, and then the nice little steel alcoves, I was impressed at the attention to detail, and then when I came back through, I was even more amused to find that those architectural details were vital to the puzzle. Nice work on the stairs too - hearing them collapse behind me, then spinning around to see myself trapped was a cool effect.
The one weird thing I noticed, mostly by accident, was that the surface beneath the large fan is portalable. When I discovered that, I thought it might be a path to a secret passage or something, but since it's a dead end, it seems more like an oversight. Although I realize that if you had some kind of physical entrance/exit to that space, it would no longer be possible to trap yourself by jumping onto the fan grille from above, and that might be worth considering.
