Three things I didn't like in order of importance
1. Girls and the love plot. i liked Columbus a lot, but I didn't like him in relation to Whichita whom I found extremely annoying. I didn't care about the love story or the girls characters (younger sister wasn't that bad in herself but without the older one she serves no purpose.) It was not interesting to see them get together. I much more enjoyed the interactions between the guys and the zombie plot and I think it would be so much more enjoyable without romance and those two acting cool. W was tedious.
The whole part in amusement park was so stupid on their end as well.
Also, how great would it be if Woody just killed them after the first incident and surprised us all who knew where it was all going? It would have been awesome, and its a missed opportunity in favor of keeping the old formula. It would have been a great survivalism point and add even more to Woody's character.
2. Bill Murray. It felt like it was there just because BM is so cool and let him do something random and cool in this film as well. But it was pointless and the whole part in his house just took from a story (of course that is where the stupid romantic moments happened too.) I get this movie wasn't about being super realistic and serious, but that just totally ruined it and really took from the story completely.
3. I don't think they needed to make Woody's sad story switch from a dog to a child. Losing a dog can be just as traumatic. And it would be more interesting for me. I didn't have any emotional switch when it was revealed it was really his son, as I already sympathized enough, and it was like it trivialized losing a dog. Ok, I get that most people might disagree with me here, but for me it was an unnecessary element. Also looking at him as a dad put me off a bit, it didn't really fit him in my opinion.
Otherwise, i thought it was real fun to watch, I liked the guys a lot, Tallehassee was fun and Columbus was very cute (but would get extremely annoying when obsessing over that girl, and like someone else mentioned to me while we watched, kept making faces like he is smiling and crying at the same time when around her.) There were really good moments there.