It's one of the few "open world" games I've really enjoyed. Tons of fun to play, and destroying the buildings is a great way to kill time.
I have noticed the physics on the building destruction is well dodgy though. I've seen buildings stay standing with just a pipe holding it up.
I've only spent 3 or so hours on it so far, but I put it on for my friend to have a quick go on yesterday, to see if he wanted to get it, and he spent half the day on it. So I guess he loved it too.
Maybe I'm doing it wrong, but what cover system?