Gosh, guys, how do you KNOW? You know... when you're IN LOVE? Probably when a trailer makes it instantaneously clear that you should be with Paul Rudd instead of your jerk boyfriend Owen Wilson, Reese Witherspoon. That's how you know, apparently.
That said, this doesn't look bad at all if you can ignore all the trite rom-com bullshit. Who can resist a Rudd? I sure can't. I'm going to buy him a house one day.
Finally, the Overnight Delivery reunion Earth has long demanded.