It's definitely coming together, but the difficulty, stability (bugs), gameplay, and content do need some work. The zombies are more like aliens, glitch out as they run around, and generally just freak out on a lot of gemometry.
Gunplay isn't super bad, but some guns just feel horrid to use (shotguns, svd). It takes way too long to be able to shoot again after swapping weapons or melee-ing. You're so OP after a few rounds that there's basically 0 difficulty after a bit. Second you pack-a-punch a gun you're basically invincible. Power ups will spawn outside after killing zombies leaving you just standing there like an idiot staring at them, unable to get them.
I want to stress though, the bones ARE there! There is potential here. I would recommend to the devs that they just polish it up then add more content. It'll be a staple of S&Box if they do so.