Creative thinking... (Spoiler)
There is one instance of the game I actually solved a puzzle in an alternate way then Valve intended it, on my first playtrough.
Some of you might remember this specific room, right after the rocket launcher:
http://www.xs4all.nl/~dianajo/escape_010000.jpg
Yes, the vent was too high. And there was no obvious way to get in it at first glance...
So I eventually solved it like I would in real life:
http://www.xs4all.nl/~dianajo/escape_010001.jpg
But now that I've listened to the commentary in the game a few days ago, I found out that it wasn't meant to be solved like that. But rather like this:
http://www.xs4all.nl/~dianajo/escape_010002.jpg
http://www.xs4all.nl/~dianajo/escape_010003.jpg
http://www.xs4all.nl/~dianajo/escape_010004.jpg
Now I've been reading around some articles on the web. And it seems that my original solution is actually more popular than the intended one. I was wondering if this is the case on this forum aswell.
-Thinking with portals
-Killing with Pyro's
-Defending with Engineers
-Healing with Medics
The "Valve" way seemed intuitive to me. That's what I did on my first playthrough. On the other hand, a friend of mine got stuck for an hour on that puzzle, and would have stayed there if I hadn't explained the "Valve" solution to him. A second friend actually did something similar to what you did, except by stacking computers instead of the chair.
I would say both are viable, but the "chair" solution is a more conventional (read: real-life) way of doing things. The "Valve" solution is, I would say, "thinking with portals."
It's like writing code in a procedural or OOP way. You can get do some jobs one way, and some the other, and some can be done both ways. It's all in how you approach the problem.
Yeah, my first playthrough I used the rocket turret to do the dirty work to blow up the tube.
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first i used the chair, then like a idiot couldnt figure out where to go once in the vent, so i went back and blew open the tube, then figured it out with the box once i went back to the fan. so i guess i had to do it both ways for me to get it. 
**edit** i also heard you can break the tube by putting a chair/object in an infinate loop then shooting it into the tube. haven't tried it, so dont know for sure.
Lol, this part confused the hell out of me. I tried a bunch of stuff, then I rememberd, "Hey, there's a rocket launcher in there!" and naturaly, glass + rocket = kersposion. 
I almost gave myself a stroke trying to figure out that level. Me and a couple friends started the game at the same time, racing through it. I was kicking ass by almost fifteen minutes until that level, then I tried for so long to make a portal close enough to jump from into the vent. Needless to say that didn't work and eventually I went and got the chairs.
I used a chair also. Weird that, we think with the same Portals.
I used the rocket. Don't think i even thought of the chair, since objects randomly fall over with the ragdoll physics.
ahh yeah this level.
I also used the chair, however I was talking with one of my mates, and he said he also used the rocket!
The chair just seemed intuitive to me, you need to step up, well use a chair!
but i guess thats the beauty of this game, there are so many ways to complete every puzzle!
I remember reading on gamefaq after I beat the game that people were using chairs and computers, but on my first play through i was trying to portal up there and couldnt figure it out, finally remembered the bot was there and blew the thing up 