Finally! Took long enough. (Although I only did a little at a time and sometimes went many weeks without playing.)
Alex helped me a lot. He sat with me and excitedly jumped up and down and provided running commentary for at least half of the time I played.
There is still the multi-player mode though…
Edit 2012 May 6 19:15 UTC: Just checked and saw that Portal 2 was released on 2011 Apr 19 and we got it on the day it was released. So it took me a couple weeks more than a year to finish this. Nice and slow I guess. :-)