Just finished the map. Not at all what I was expecting. You didn't try to sell me didly squat. Where's the hair in a can? Where's the super blender? Or the knives that just won't dull!? WHERE!?
The map seemed unnessesarily large. Lots of open space where the player can mess around in. At times I was looking around for a place to go.
The companion cube, I took it everywhere I went. And I'm glad I did, as if I did not, i'm pretty sure I would not have been able to get it back.
You mentioned a ramp fling. I'm pretty sure I did that wrong.
When you stand at the bottom of the ramp, you can just barely see the portalable area at the end of the glass walkway. I just portaled to that, and took my cube with me.
One thing I found slightly frustrating: The various sets of stairs that you need to the WCC to go up; They're very thin. Not enough room for you and the WCC to be on comfortably. I mean, yeah it can be done. But you need to struggle with it to get it into just the right spot. Otherwise it'll fall off. I can understand wanting to put a little challenge into things. But they're stairs.
There was also a Step up type portal (I think it was the last one that you need to do.) That I for some reason just had a hard time with. I'm quite familiar with this type of technique, it's actually one of my favorites. But this one, I just always had a rough time starting it. I think you might want to lower the bottom step, or raise the top step. So you can gain a bit more air in your first step-up.
Other than those gameplay aspects, the rest of the things that I noticed were pretty much aesthetic;
Impossibly thin floors, Platforms that seemingly just float on the map, constant use of the same texture.
And you've already stated that you're working on some of the textures/lighting etc.
Overall, I'd say that you did an amazing job for your first map.
Edited to fix spoiler tag mistakes.