A week ago I would have given this a fairly mixed review. I was reliant upon other plugins for my Zombie spawning needs and all of them are broken except for this one. While there are plenty of features and fixes I would like, this plugin is one of the best and compared to BotRespawn, one of the cheapest paid NPC plugins.
A few current issues with the plugin at the moment: Zombies float slightly above the ground, no option to have zombies spawn near players so they always have to pepper the map in the thousands for the full effect whereas a few hundred in the right place would serve the same end. Zombies prefer to play follow the leader rather than chase down the player, they operate better as single zombie hordes. Zombies get stuck on cactuses and become immobile. Zombies sometimes cannot hit animals due to being too close.