1. Joseph Gordon-Levitt is one of those actors for whom I find it nearly impossible not to root. He has an inherent, innate likability about him that doesn't seem forced, calculated or manufactured; he's a labrador puppy you have beers with. Now, I don't know anything about Joseph Gordon-Levitt in real life. He seems like an affable, friendly sort, but he is of course paid handsomely to project such charm and relatability. If I found him dour, indifferent or cruel in his public appearances, he wouldn't be doing his job. But this is sort of my point: Gordon-Levitt has such star power, such leading man potential (he's got vintage Hanks crossed with vintage Cruise in him), such undeniable engagement, that you have to remind yourself that not every character he plays should necessarily be so likable. The world isn't full of Joseph Gordon-Levitts. This is a bit of a relief.
2. Don Jon, Gordon-Levitt's first film as a writer and director, has energy and gusto and a plaintive eagerness to please in spades... but I'm honestly not sure it should. This is a film that should have darkness in it, should be willing to dig deeper beyond the surface eccentricities of its hero, to find out who he truly is and what might be behind. But the movie—and, one suspects, its star—is a little too sure of itself for that. This means to be a tale of a guy learning more about himself and how to be a better person. But I don't really think the film thinks he needs to improve all that much. And the character is so muddled that it's impossible for the audience to tell what exactly he needs to improve on, if anything.
3. He's of course still likable, thanks to Gordon-Levitt's lively, cocky performance as Jon, a Jersey club kid who just wants to work out, pick up girls, go to church, and watch lots of porn. (Think "Gym. Tan. Laundry. Masturbate. Confess. More Laundry.") His life is basically simple and easy until he meets Barbara (Scarlett Johansson), a Jersey club girl, but a "good" girl, one who just wants to "domesticate" him so they can buy a house and have a family and whatever else she wants him to do. Barbara is repulsed, though, by Jon's porn addiction, or whatever it is, and she demands he stop. When he doesn't, and she breaks up with him (and this is actually the plot development: she finds out he watches porn and immediately ends the relationship), he takes solace in an older classmate at his night school (Julianne Moore) and her tragic backstory.
4. Part of the problem is that the movie doesn't really ever figure out if what's behind Jon's "addiction" to pornography, or whether there's even anything wrong with it at all. There's no sense that Jon's background has given him a warped view on women—his family is a grotesque, if occasionally amusing, cartoon—and you can never tell if the movie thinks he watches too much pornography, or if Barbara is just a tight-ass who makes too big of a deal out of it. Pornography, weirdly, is treated as a plot point—it's how Moore introduces herself to him—and then discarded, like a tissue, when the movie has decided it doesn't need it anymore. This is supposed to be a coming of age story for Jon, but I'm not sure what his journey is supposed to be. Is he supposed to watch less porn? Is he supposed to avoid man-trapping stick-in-the-muds like Barbara? Is he supposed to just have better sex? Because we never get a sense that Jon really needs to grow up that much at the beginning of the film, there's nowhere for him to go. It's just a bunch of women trying to mold him into something, and him fighting them off. Jon's arc isn't an arc at all. It just zig-zags all over the place, bouncing around everywhere, and then the film ends.
5. The movie's still entertaining. Gordon-Levitt has more propulsive momentum as a director than self-control, but he's so energetic that the movie carries you along even when it probably shouldn't. He and Johansson have undeniable chemistry—you can tell she loves getting to play a gum-snapping va-va-voom Jersey girl, albeit a prissy one—and even when the movie isn't going in any particular direction, it's always moving. There isn't, though, anything close to any sort of overarching message about masculinity, or technology, or relationships that the movie seems to want there to be. The screenplay can't just settle down and tell a story; it's too busy hopping all over the place, eating every piece of candy it finds. It all still works, in large part because of its likable lead. But he should probably find a different writer next time.