Basically a question for those who have completed it and mainly about timing.  Is it all one - person does this then the other does something else - like the early levels show or later on do you you really need the two people to be acting in concert.  i.e. is pass and play with 2 controllers feasible (albeit unlikely to be much fun).

By about the 15th chamber you'll need to be doing things at the same time. So no, not possible on your own I'm afraid.

Maybe with pausing?

No one I know has Portal 2, so the only option I have is to try to persuade my older brother to play split screen co-op with me. You know how hard it is to get someone who's very set in his ways to play Portal?...Extremely. 

" By about the 15th chamber you'll need to be doing things at the same time. So no, not possible on your own I'm afraid. "

I'm up to course 3, chamber 6. And this is where I'm starting to suspect that I may need another player. Up to that point hough, there haven't been many problems.

Not sure if anybody's still reading this, but I was able to play thru co-op by myself. There are a couple stages that are quite challenging trying to work two controllers at once, but it can be done.