Just finished Trine. But one thing I did figure out, even on my 2010 MBP i7, if I ran it in windowed mode, it sucked, it just wasn't smooth (but I had everything turned up).
Trine offers a ton of video settings to tweak to adjust performance, I'm sure you could get it to run reasonably well by making some compromises.
As I said, I just finished the game, it was fun; but often frustrating. The last level was an effort in insanity, there was no reason to make it that screwed up. Even worse, is you can get through all the hard parts but if your wizard is dead or has no energy left; you have to start over. Really lame. There were some "stupid" parts in the game and thus the 7 out of 10 stands. I would have given a higher score if those lame things were not included. Note to game designers; have to jump, in the dark and land on a small square or your character is instantly dead, isn't fun.