Hard to believe there's only one other person commenting here who remembers Don McKellar's fine "Last Night" from 14 years earlier, which already tread on similar ground but without the dubious sentimentality. The cuteness is watchable, if you can afford all the empty calories.
This is a considerably uneven comedy, trying to mix dark (and sometimes crude) humor into a story that tries to respect the emotional gravity of an apocalyptic situation. Still, those elements apart from each other are pretty entertaining, so I did enjoy the film overall. I laughed a lot, I thought the emotional scenes were handled and played well, and I willingly followed the journey the whole way through.
Comparing it to "Melancholia", this is a funny, yet realistic approach to the end of days. Quite enjoyable, but certainly not special. It is sad to mention, but Keira Knightely and Steve Carell together just doesn't have the chemistry to make this film memorable.
There's too little that feels wrong with this movie. It's sweet, at times funny, the cast has chemistry and the premise is interesting. And yet, there is nothing about it that manages to surprise. I just can't imagine having any particularly interesting conversations about it.