On Rotten Tomatoes, the consensus reads: "Greenberg's title character is harder to like than most, but Ben Stiller's nuanced performance and a darkly funny script help take the misanthropic edge off." Kurt Loder of MTV News wrote, "The movie is set up as a quirky romance between two lost souls, but in the end it seems more like a stalemate than a love match." David Edelstein of New York Magazine lamented: "Greenberg would be a heckuva movie if we could just get Greenberg out of there." Christopher Tookey of the Daily Mail was perhaps the most harsh critic of the film: "This is the kind of low-budget movie that attracts respectful reviews, but tiny audiences. That's because there's virtually no story or character development and the main character's an idiot." The main issue with "Greenberg" is that Roger is so unlikable it's quite impossible to root for him. He is polarizing, hurting and hurtful. His mental issues manifest themselves through various phobias and idiosyncrasies, which points to the fact that his is just afraid of life and of taking risks that could possibly lead to failure. He avoids large groups of people, writes endless letters of complaints to companies he feels have somehow screwed him over, overreacts to other people's words and actions, and makes a general antisocial and sociopathic pain-in-the-ass of himself. He is as well psychologically abusive to Florence, that carries her own share of vulnerabilities, whom he keeps pushing away with his eccentric behavior. Throughout the film he is a pain in the ass for everyone around him and you quickly realise that Roger is just someone you would´ve cut out of your own personal life. Why the other characters don´t do that, like Ivan, is a mystery to me. He makes himself so hard to like and he can´t see why people don´t like him alas no knowledge of the self. There´s moments when he actually shows a deeper understanding of his ways and actions, but not enough. He never reaches some sort of closure with himself. Even if we are told that he just been released from a mental institution, you simply forget about that in the equation as the character development is static and we see no real change in him. And when you put together two socially challenged characters as Florence and Roger you need a greater dynamic which is missing here in my point of view. Greta Gerwig does a great job as the physically and emotionally awkward Florence, while Stiller is just playing an akward moping Stiller in a way. Noah Baumbach tries to put another spike into indie heaven, but his progressive story is all over the place with no real direction. The attempt to adding some black comedy doesn´t work either. Do we care what happens with him and Florence? Do we care what happens when his brother and his family comes home? Do we care if he manages to actually patch up things with his old bandmates and maybe start playing again? I reckon my answer is no. "Greenberg" fails due to that fact that the film makes it too hard to identify or empathize with the characters, especially Roger, who is just annoyingly self-indulgent and nothing else.
The cast does pretty good work here. For the most part these are all good characters, despite their obvious foibles. Even Ben Stiller is commendable in his role. In fact, Stiller's protagonist is so out-of-the box insane that he transcends the usual cliches you'd normally associate with a narcissistic, manic-depressive, free spirit in an indie dramedy. Whatever his mental disorder, he thinks and reacts in such random, unthinkable, deplorable ways, that one can't help but find this portrayal refreshing (thankfully, the people around him also react appropriately to his anti-social behavior). This also makes him feel more genuine, like he really is capturing the tortured state of mind of a real segment of society.
Equally important, the script is strong. It is often quite witty, and it offers plenty of interesting (again, not cliched) situations in which to demonstrate the disorder of Stiller's character's mind.
But boy, this character fascinated me so much; the movie is so engaging to watch because we all know people like him, and Stiller gives his best and most nuanced performance of his career. Greta Gerwig, Baumbach's muse, is so damn likable and approachable as Florence. I love everything she does and she is really good in here. Rhys Ifans also does a great job as Ivan, Greenberg's ex-band mate. I loved Baumbach's direction and his darkly comical script, which was co-written by his then-wife Jennifer Jason Leigh. He skillfully walks on the thin line between humor and heartbreak. Greenberg may be hard to watch, but it is definitely worth seeing.