Pretty good, but rather slow...
I liked the whole concept of everything, taking care of all the different categories at once and whatnot. But it never seemed to get difficult, or even advance the gameplay. It was just get survivors, make soldiers, defend and expand as I could. I'd have liked it more if it were real-time, I think that could up the excitement quite a bit, having to think rationally in a short period of time would make it more like a zombie apocalypse simulation rather than just a top-down game that happens to have zombies. I may just think this since I honestly only played on normal, but I can't imagine hard being much different other than you'd expand slower cuz you'd need more soldiers.
I tried playing for a while, but I may have still missed some stuff, but from what I saw disease would just kill someone then leave. I think it'd be more exciting if it became a legitimate problem and doctors had to be trained, too. Also, if you could upgrade everyone to be more effective rather than just selecting 30 soldiers to guard your town. Also, I know it may be against your whole idea, but I think switching to a tower-defense sorta thing for defending your town every time zombies came by could break up the slower parts. These are just ideas, though, they could very well not work out.
Finally, with the randomish survivor names and joke-y line here and there, I though it would be neat if there were some referenced to famous soldiers, leader, scientists, etc. So there's my two cents, I'd like a sequel regardless of whether or not you necessarily follow my ideas as this game was pretty enjoyable as I started getting into it, it was just the big picture seemed pretty repetitive.