Everything is very realistic. Get shot a few times and you're dead. Animal attacks you once or twice, you're dead. Get set on fire or crash a car, you're dead. The side missions can be quite repetitive, but still fun. Overall, good game, looks beautiful.
There are so many good things about this game--I wish I could give it a good review, but I can't. The game looks great, the scenery is fantastic, it has an interesting story line, and it could be a lot of fun, except for a few irritating details.
First, it has a problem recognizing that you are standing right on top of something useful. It even knows the items are useful, since it highlights them with different lighting. It is really irritating spending several minutes moving back and forth, pressing reload while standing right on top of the flamethrower canister needed to reload the flamethrower in your hands. This should be almost automatic.
Having to repeat a section over-and-over until you get the sequence just right to satisfy the script is irritating. Easy mode should be relatively easy. Save the hard to figure out puzzles for higher levels. And another thing, the autosave does a lousy job of saving checkpoints in a mission. If you shutdown after a checkpoint in a mission, you should not have to complete the previous checkpoints when you come back later. This is just stupid.
Also, although there are cars everywhere for you to just steal, the scenarios have you go from one side of the island to the other, then back to the other side, then back again. Completing side missions as you move toward a goal would be a lot more logical. The game is a very disorganized.
Other than that, it's a fantastic game that could be a lot of fun. I just gave up, because it wasn't fun anymore.