At the rate me and my girlfriend are going we may finish this by Christmas! Today we completed the campaign 'Airdrop' mission which introduces night play and the Blade 2 ripoff zombies who's cone of vision is visible on the mini-map so I guess I'm still doing the tutorial intro missions! Since we completed this mission the game seems to have inserted some new zombies during the day.
The first inkling of this was when moving around the buildings north of the tower near the first safe house you unlock. A little pop-up and tells me the noise I'm making will attracts 'virals' then two of these screaming weirdos start climbing up to my roof. Luckily it was a high roof and a boot to the face and a drop kick put them both all the way down and out. Later we came across a female zombie welding a pipe - we've now seen a few of these. Then there are zombies on fire who don't seem to die, nor do they fire to other nearby zombies unlike zombies you ignite with molotov or burning throwing stars. Exploding throwing stars do the trick, though
Although we've not done much in the campaign we're around lvl 4-6 across the skill trees just due to running around, looting, crafting and smacking zombies. It's seem impossible to run out of items given the two quartermasters give away a bunch of stuff every day and all the crates, boxes, refridgerators and other containers seem to reset every couple of days. The people of Harran sure like their coffee.
We've found a ton of blueprints for equipment and weapon upgrades and my girlfriend found a 9mm pistol in a hut by the shore, although we have no ammo. Although it's worth $9,000 we're resisting the urge to sell it because we're finding lots of green weapons and a few blue ones too.
We're really ending this game - it's fun just running around, walking zombies and scavenging. Had the game about three weeks, have done three campaign missions