Got the game for $25 over Thanksgiving weekend, beat it a few days ago. Honestly its (lack of) performance seems in keeping with its quality from my point of view. Enslaved is a game that had a lot of potential but ended up being a disappointment for me. Until about halfway through it's one of the most beautiful games ever released, then the environments change and it looks ugly and awful. The high quality of the voice-acting wasn't enough to compensate for a dull script and lifeless story - I understand that they wanted to avoid sappiness, and they did that, but the relationship between Monkey and Trip isn't anywhere near as well-done as that between the Prince and Farah. The combat is absolutely atrocious throughout, let's not even talk about the bizarre platforming.
There were things I liked about the game (including the ending, which I thought was spectacular albeit a total non sequitur), but in the balance it's just not very good.