Yeah, when I checked my save game it showed 17 hours game-time and (I think, can't remember now) 15% complete. It is a pretty HUGE game and you are free to do whatever you like whenever you like. Sometimes I just mess about for an hour or two, exploring the world and blowing shit up. :p
Also, don't know if you know this, but the island from the LOST tv series is in the game, or at least a "tribute" island. It's the island in the top left hand corner of the map, if you fly over it your plane catches on fire, same thing for boats. You can also find the LOST plane wreck as well the hatch there. I have found the plane wreck, but I haven't managed to locate the hatch yet.
There is a story, but it isn't really that good. It's very cheesy and kinda lame, just like the voice-acting, but I have to agree with Neo, it does feel right for this game.

