[quote name='panzerfaust']my problem with the singleplayer, however epic the dialogue and ending were -- is that it was simply too much. the middle and later portions in the game really dragged a lot.
it was like playing the original portal, except it's 3x longer.
i did love the game, but it became a bit tedious at times.[/QUOTE]
If you play with the commentary on, they start to talk about that towards the end. They knew it was dragging, and the play testers said it was dragging. They tried to add those segment in the end where you ride the line of light for a while between puzzles to break the flow of the boredom, but it didn't really work.
I wanted to fault the game for that- but I got over it. I felt like it dragged at the end, but really it was just too complicated for too long. If I'd played it in shorter sessions i might not have even noticed.