I really quite strongly disliked Dying Light for the first couple of hours or so, it just felt a bit bland and 'meh' for a better word. After that something clicked and I wound up really, really, reeeeeally enjoying it and spending many hours with it. So final verdict is yup, it's great, but you might need to get over the initial hump first. The DLC story expansion is quite sizeable too so that's a really good price for a lot of game.
I think it might have been playing some co-op with a friend that turned me around on it, started to see the fun side and it all felt a bit less dreary after that.