Simply put, the combat is a little clunky. First-person melee combat is hard to get right, and like most efforts, Dying Light can quickly become an exercise in frustration. I died on numerous occasions simply because I thought my weapon would hit a zombie, and it didn't. Even when it works, it doesn't take long for the novelty of hitting the zombie with the pipe to wear off. You'll also frequently end up grabbed by zombies and facing that most-dreaded video game foe, the quick-time event. Perhaps a better word for it is tedious.
Compounding the problem is a quest system that is filled to the brim with fetch quests that send you all over the map to retrieve items and bring them back. Sometimes, you'll be sent to find a clue, that leads to a clue, that leads to an item that you have to bring back. There's very little variety in the missions, causing them to quickly feel repetitive. Adding to that is the fact that you end up running back and forth across the map in nearly every mission, since there's no fast travel system.
Outside of killing zombies and running fetch quests, there are plenty more things to do. There's a fairly basic crafting system that lets you make items like medkits and flares. There are radio towers to climb, items to collect, and all the things you'd expect to see in an open world game. It's just that none of them are done in any unique way. They feel like filler; items that were added in to make sure they were there to fill the box on a checklist.
It's a shame that these problems exist, because they distract from what could be the core of a great game idea. For all its faults, there are a lot of interesting ideas in Dying Light. The day/night cycle is a nice addition. Nightfall brings out the Volatiles - pale, naked zombies that are faster, stronger, and more dangerous than their peers. They'll also alert other zombies to your location. Once the sun goes down, the choice to venture outside is a much more deadly one. It's more rewarding, though, as experience points are doubled at night, meaning you'll be weighing the risks each day at dusk.
The parkour system works well when the controls cooperate, and the idea behind it is solid. Rather than make a game about fighting zombies and parkouring around the city, Techland may have been better served to focus on the navigation and avoidance that feels so good here and less on the "fighting zombies" action sequences. Much like Dead Island, Dying Light just breaks down a bit once you've played if past the 15 -20 hour mark.
In the end, it feels like Dying Light is a 15 hour game that was stretched out to 40 hours. There are good points in the game; they're just buried under a lot of unnecessary busywork. I was hoping for Mirror's Edge with zombies, but I ended up with Dead Island with parkour.
Bottom Line: Dying Light isn't a bad game, it's just one that feels like it goes on a bit too long, and was too invested in the trappings of an "open world" to make itself really stand out.
Recommendation: If you're a fan of zombie games, liked Dead Island, or are really into parkour and open worlds, you'll have fun with Dying Light Just don't expect anything new and groundbreaking.