What I really liked about this game was the detail that went into the included parts of the television universe and the very much in-tone storyline. Elliott seems like he could have been a main character on the TV show for the past three seasons, complete with his own arc as he struggles to learn who he is and who he doesn't want to be anymore.
The locations like the Black Rock, the survivors' beach, all of the DHARMA stations, and the jungle are all exceptionally well done, combining with the music to create a very much 'Lost' atmosphere. The smoke monster is actually pretty frightening, mostly because you still have no idea what the hell it is. And don't even get me started on the ending, I thought it was awesome (especially after having seen last week's episode 405 "The Constant") and truly earned the game the right to call itself Lost.
I could have done without the caves or the trading system, because the way they were implemented was very rudimentary and not involved in the story at all. Then there's the length. I bought it for my PC on Saturday afternoon and beat it in about 10 hours. Then, today, I got up and played the whole thing again and unlocked all the extras in about 5 hours. This feels like the demo for the game we should've gotten. Considering we could have had the entirety of the Island at our disposal, this game could have been 5 or 6 times as long. 70 days on the Island go by in 6 episodes? I don't think so.
So to sum up, the graphics were pretty good, the music was awesome while some of the voice acting was mediocre, and the presentation was fantastic. If I were you, I'd just rent it for the 360 and blow through it in an afternoon. Hopefully they can release more episodes, or a new expansion pack or something.
If you're playing it to expand on your level of fandom from the show, you'll love it. If you're playing it because you're expecting a fantastic game, you probably won't.