How long did it take you to beat Portal 1?

First time, without knowing mechanics - about 2.5 hours.
Second - about 40-50 minutes.
Third and onward - about 25 minutes, excluding runs for achievements =)

Slightly under 2 hours.

Something like 2 hours at most, taking it slow. I should try a speedrun of it, might be interesting to see how it turns out as I have yet again forgotten most of the puzzles. Might be easier after playing through Portal 2 though.

I do believe it's an amazing game nonetheless!

I ran through it again for the second time since release recently, completed it in less than 2 hours, no idea how long it took me first time, that was before steam logged hours played.
It did surprise me realising how short the game was again, also, they changed the ending since it was released!? the last time I played it had its original ending...

Two hours, now i'm doing the advanced test rooms

A few hours, have forgotten how many exactly. Now I have got ~30h. ^^'

After many attempts I can finish Portal in around 35 minutes.

my first attempt, just few days ago, i finished in around 1hr 10mins

1.1 hours.

About two hours the first time and now I can beat it in around 50 minutes.