Open world games are my fav, along with this and the chance to play "a Ghost" is really my cup of tea.
I've enjoyed the first zone so far (I'm a dad, so game time is very limited) but the map is quite beautiful and so far, the weather has felt dynamic and realistic. That's a very nice detail! I can't say how much I enjoy the sound of the doors opening and closing on cars and the sound of the rain hitting things. It's a very nice detail.
I've got some issues with how some of the vehicles feel weightless and the helicopter controls are a bit wonky but if you just figure out how they work, they're not a big problem. I can't say that any of the physics have really made me enjoy the game less.
I've seen a lot of people complaining about missions failing when you get detected, and I can't agree fully with them that it's a bad thing. If you take a nice slow approach to most missions, you'll get in and out fine without any hassle. Just plan it out, recon the area a bit and just be silent. I felt like I was really working towards taking El Sueño down bit by bit by bit.
Those are my two cents and I'd recommend this game to anyone who's like me, really.