With all games I like to give them some time when they are just released. The reason I do this is to let the feedback on the game help me to make my decision. The problem to me with Just Cause is that it seems like a game that was created "just cause" they could. In the game I feel really lost and don't know where the story is going.
On the other hand though I will tell you that I think the grapple hook in the game is really cool and I was watching a video on youtube the other day that showed some new features. For action I think the game has a ton of it! I will let maybe a week go by and then get it.
I already pre-ordered it and I'm waiting on playing, I think the game will be really good so I want to support the developers as much as possible. They were really great in socializing with their playerbase and adding some people's ideas.