Not to be confused with the book What If? by Randall Munroe. (Which I got for Christmas, thanks very much.) And, despite the title, it's not one of those imaginative movies that explores what someone's life might be like if they'd made one simple decision differently. Instead, it's a nice little romantic comedy, and it's perfectly OK at that level.
As you can probably tell from the Amazon link image over there on your right, one of the stars is Harry Potter himself, Daniel Radcliffe, playing a slacker named Wallace. You might be less familiar with the female lead, Zoe Kazan, who plays an amiable goofball named Chantry. (She's Elia Kazan's granddaughter.) The movie works due to their winning chemistry, and above-average dialogue.
Mr. Radcliffe is British, Ms. Kazan is American, so (of course) the movie is mostly set in Toronto, with them both playing Canadians. (According to Wikipedia, there was a minor controversy about the movie's "entirely caucasian cast". Even though Toronto has, using the language of modern racial pigeonholers, a 49% "visible minority population", they're invisible here.)
Anyway: Wallace is in a lengthy funk from his betrayal by his previous girlfriend. He meets Chantry at a party, and is enraptured by her clever banter. But she lets him know right away: she has a boyfriend named Ben (a nice guy), so it's strictly a let's-just-be-friends deal. So that sets up the conflict: Wallace doesn't want to break up Ben and Chantry. But he doesn't want to lose her either.
There is the usual array of friends and relatives, all happy to offer advice and to serve as plot devices.
As near as I can tell, this movie spent about 10 minutes in theatres before going to DVD. Is it impossible to make a financially successful PG-13 romantic comedy these days?