This is probably poorly timed, considering the work we're doing on the space game, but I can't sleep and wanted to get this on paper. So to speak.
One thing I like about the zombie survival genre is the universality of it. That is to say, every time you see a zombie movie, it's not just localized in one area, it's a state/nation/worldwide problem. Resident Evil was something of an exception that hard and fast rule, but there you are. Ultimately, what I'm seeing with this is that any ambitious (or unambitious) GM who wanted to run this system could go to City Hall, get a city or town map, plunk it down, and say "Here's where the game is set."
It also strikes me that there would be one main goal. Survive. Of course, there are several subgoals that would be integral to the game. Looking at the movies, there were several issues that were "do-or-die," as it were, such as travel, supplies, food & water, communication, figuring out where the holy heck these undead brain eaters came from, etc. Of course, the figuring out aspect would be more of a campaign goal than a short term survival goal. Which brings me to my next point.
We've discussed the idea of universality, running Zombie Survival: Skiatook and Zombie Survival: Tulsa basically being the same thing. Here's where it could get really interesting. Applying the same universal idea, you can start a game in Skiatook, Owasso, Tulsa, etc., and wind up pretty much anywhere, with the same problems, of course. Moving from one building to another would require a check to see if there were any zombies, and if so, how many, etc. Town to town travel would be a la Mad Max with a few undeads thrown in for good measure. Also, you have the idea of early vs. late infestation. Early zombie infestation would have fewer zombies, more humans, ostensibly less trouble getting around, but more competition for needed supplies, possibly leading to human vs. human violence. Late infestation means not only more zombies, but also opens up the possibility of more advanced ones. An interesting discussion that's popped up of late is the difference in zombies now and in yesteryear's movies. The original Night of the Living Dead had the zombies as slow, shambling creatures, where the most recent Dawn of the Dead (don't bother renting it unless you just want to be insulted) had the zombies being able to use a full range of motion, including running, climbing, opening doors, etc. Let's say just for the sake of argument that the "zombie problem" is caused by a virus. Okay, so the virus mutates. It still destroys the part of the brain that controls emotion, morality, aversion to brain-digestion, etc., but leaves the motor functions alone.
Again, this is all wild speculation, but I couldn't sleep and I thought getting this out of my head might help. Feel free to post constructive thoughts or haranguing insults at your leisure.
Consistency - It's not just a river in Egypt.