I didn't love every single part of it, but I can't recall a part where I was particularly disappointed with anything. In fact, I'd argue very much against making it longer simply because then I believe you'd begin to encounter the sort of fluff that would then ruin the movie's pacing. I thought Zombieland was pretty freaking awesome from start to finish. I didn't even mind the whole obligatory infusion of the romantic subplot, although I imagine that would become the largest source of ire if there is one at all.