Ive seen alot of others say things about how it crashes/freezes up. I have had no such problems from the moment i got it, which may or may not be attributed to it running on a brand new MacBook pro.
The graphics certianly arent the best (very polygonal being a gen. 1 port) though they can be easily forgiven.
Sound wise its got an interesting soundtrack (you can look it up on iTunes) and the voice-over work is pretty spot on, with the familiar voice of Richard Horvitz (Invader ZIM) as the main character.
Controls can be a tad confusing if youre on a laptop like myself, but their tight otherwise. I never had a platforming issue where i missed a jump or fell off a cliff because of the controls. Also, all control bindings can be customized, though they will reset after you start a new game.
In my opinion the characters are well fleshed out, the story, and the inovative idea of going inside someones mind and navigating its many obstacles were superb. Examples i can give without spoilers would be a Military Vets war-zone obstacle course and a paranoid guards M.C. Escher-esque suburban neighborhood full of hidden spy cameras and G-men in disguise.
I absolutley love that it was ported to the Mac, especially since i missed out on such a jem when it originally came out.