Killing Zeds and slurping energy drinks
Loving it so far after the patches.
There is some jankiness with movement but that will likely be fixed with upcoming patches, as long as the developer continues supporting it. The gameplay has been solid and reminds me of all the good aspects of Borderlands combined with a bit of Fallout 3 and Left4Dead.
Combat is tight, visceral and when playing single-player there's this feeling of dread that not too many games get right. Multiplayer is awesome when playing with one or two players.
The underlying RPG elements are well integrated (love building odd weapons) along with a simple loot system. For the most part zombies level up with you.
To increase your health you consume things like energy drinks and apply medical bandages.
It's imperfect but extremely fun and immersive.
Tip: Turn off the arcade indicators like Names\Health\etc. (in Game Options) and you'll amplify the experience.