While half of the zombies are incredibly fast, unlike Left4Dead, you will not be facing huge hoards of them for the most part. (Don’t be discouraged… this is a good thing) Rather the zombies are really agile and strong. If you suddenly walk up and have 5 zombies coming at you full speed, you are in trouble. This makes the game not only a hack and slash type game, but you have to have a little strategy in how you are going to attack. Death will cause you to lose money, and if you threw the weapon you were holding, it most of the time is gone when you get back there (in Single player mode).
While there are vehicles in the game, the handling for them is not that good. You remain in the first person view and can look around as you drive, but the turning is terrible. There were many times where I got stuck and had to perform an Austin Power U-turn. I think Techland sought realism, but I would rather just walk or use the fast travel system.
Probably the most amazing new feature in this game is the multiple layer damage that can be done to zombies. Every zombie not only has skin that shows damage, but their bones take damage as well. Grab a baseball bat and hit their arm just right, and you will break the bone. As they continue to attack, you see that broken arm dangling to the side, unusable for the zombie. Break both arms and the zombies still try to charge and bite you.
The map is huge, so you have plenty of space to explore. And then once you cross into the city, you find out that the first map you saw is only half of the playable area.

Dead Island Multiplayer/Co-op
Many people will find this game to be fun in single player. But the real fun is having a good team. The more people playing, the more zombies and the higher they are leveled. And Techland took a few steps that I think are in the right direction to make the game fair.
For instance, if you throw a weapon, the game has a 5 minute timer before the other players can pick it up. This prevents you from throwing an awesome weapon and someone just snatching it up. Similarly, if you open a crate or luggage, other players must wait 5 seconds before they are capable to taking the items. This prevents people of being item whores. There is also a built in trading system. You can exchange weapons and collectables (like duct tape, nails, canned food, etc) without having to just drop them and let your friends pick them up. Lastly, it seems that everyone gets experience and money when their friends find it. Whoever makes the kill gets double experience but everyone gets equal shares of money.