The biggest critique here is obviously the voice acting and dialogue, Nigel just isn't a funny character, and the references to the actual Portal games only felt annoying to me, "for the people who are still alive," where have I heard that one before...
But, I do like the rest of the game. I do feel that a lot of the puzzles fall into the issue of not really feeling like puzzles but instead a series of events, there still were highlights though, Test Chamber 7 and Chapter 4's Chamber 8 were my favorite chambers. Seeing the older Portal maps, that were also seen in Portal 2, was disappointing for the game's length, but at least they took a different spin with them, since you no longer have a portal gun. So, it's not bad, it's just pretty underwhelming compared to the livelihood of Portal 2.