I don't know, I played the first game and wasn't overly impressed by it. I mean, it was fun, but it got stale very quickly, as the time constraints forced you to choose between playing the story missions and just messing around in between them or doing the story and then rattling off the side quests as quickly as possible, there was no middle ground. You were either messing around most of the time (which got old after awhile), or doing the same kind of missions over and over and over (go here, find this/them, bring it/them back to the control room) if you tried to do all the side stuff and the story missions.
The Boss fights could have been really fun, but were degraded almost to the point of simple grinding by an atrocious aiming system and clunky controls and camera. This effect also permeated to the simple act of killing zombies, too, and resulted in the game only being fun in short spurts for me.
After playing Case Zero, it doesn't seem like all that much has changed. The aiming system still blows, and the additional time constraint of having to give your daughter Zombrex every 12 hours (with only a one hour window) seems like it will be just an added hassle to those that try to complete the story and as many side missions as possible, unless you are able to stockpile Zombrex and just leave it with her so you don't have to worry. I don't know that this element will be present throughout the entirety of the main game, but any point it pops up it isn't going to be a challenge, more so just a gigantic pain in the ass.
There are improvements, however: being able to create interesting weapons is a nice touch (but on the other hand, once you find a place that spawns guns indefinitely, what's the point of carrying melee weapons?), the ability to buy certain objects will be a nice option for those that don't feel like remembering where every key item spawns, your companions seem to actually be able to follow you through a crowd and not get bogged down fighting zombies or getting bitten, and at least you are allowed to charge through crowds of zombies without getting attacked by every single one of them while carrying a companion that needs help.
But really, where's the plot going to go? At least in the first game the zombie outbreak was new and fascinating, and the story lead you to uncover the truth of what happened and who caused it, but this game just seems to be a "do whatever you have to do to save your daughter for X amount of time, game over" title. That is, unless out of nowhere you are put in a position to stop the zombie outbreak and save the city, if not the country/world.
I think I'll wait awhile and pick the game up used in a month or two, I don't think they've made enough improvements to warrant me dropping $60 on launch day, and I think the game will still become stale very quickly to everyone save the most ardent zombie-massacring sadists.
