Just a heads up to say that we have finally released the first version of PZ online, so far capable of 32 players on persistent player run servers.
You can find out more by clicking this link: http://projectzomboid.com/blog/2014/02/apzdtisa-3-this-time-with-live-multiplayer/
Remember: Consider trying the demo before purchasing.
If you're cool with bugs, and want to support the game, then we'd love to have you on board. Bear in mind any issues WILL be fixed, so if you're cool with that, feel free to buy away.
However, if the money is important to you and you want a perfectly stable and polished build out of the gate and no risk of temporary compatibility or performance problems, please consider downloading the demo, even if just to test it runs, and ensuring the game is ready for you, and you are ready for the game.