only about half the characters get their actual voices, and only one or two of the sound-alikes aren't awful.
The game itself is about seven hours long and vacillates between kinda okay and not very good. For every clever idea it has, it also possesses another three stupid ones. It is kinda neat to see all the environments and various easter eggs from the show (Hurley's Van, sweet!), but your story, the one you actually play, doesn't relate to the story of Lost much and isn't as interesting as the stuff you invariably keep cutting away from.
Also, you will spend almost a quarter of the game looking at this screen or some variation of it. I'm not kidding, half of the actual gameplay consists of this switch puzzle.
spoiler (click to show/hide)
So the game design is mostly crap, the graphics aren't terrible but ain't nothing special, the music's great, but they ripped a lot of it from the show (original stuff from the show's composer helps ease the pain though), and the story is only intermittently interesting. Any non-Lost fan has absolutely no reason to play it, and any Lost fan can get by on renting it with low expectations.
Kane and Lynch
Uncharted
Haze
and every other favored whipping boy of Evilbore, are all better games, but none of them have a guy imitating Terry O' Quinn shouting "Don't tell me what I can't do!" for no damn reason.