[Very minor spoilers...]
I guess it was OK, by virtue of staying true to its overall premise. If you're looking for a summer blockbuster monster movie, this isn't for you. It's more a small story of how two unlikely companions struggle not just to survive, but preserve what little is left of their humanity in the wake of a sudden massive creature attack. Little things like going out for pizza, and performing a magic trick, silently like Teller would, in an abandoned bar.
I caught a trace of the old Don Johnson movie,
A Boy and His Dog, but in this case would be a Girl and Her Cat. Speaking of, talk about a chill feline. I kept expecting a loud meow to give away the game at any time, but barely caught a muted mmmrrrpphhh in the final scene. The human characters showed much wider emotional range.