That whole Judd Apatow schlubby, boy-men, buddy-movie-turns-into-boy-girl-romance thing (KNOCKED UP may be the best example and Seth Rogan the emblematic representative actor) is what I expected I LOVE YOU MAN to be.
And it is, in general outline terms. But, it also isn't. Partly because John Hamburg who wrote and directed I LOVE YOU MAN was doing this before the Apatow phenomenon became dominant (see Hamburg's ALONG CAME POLLY, which he wrote and directed, or ZOOLANDER which he wrote, both before the big Apatow ascension, though Apatow's been around as a producer for a lot longer).
No one making movies, certainly not comedies, is as consistently successful as Apatow, nor does anyone make films that are as consistently well worked out as Apatow (there's rarely, if ever, a missed beat or plot point in Apatow's funny films, they're like perfect comedy machines, at least for these times and certain age groups).
And Hamburg's movies contain some of the elements Apatow uses in his (and some of the actors etc.) so I'm not trying to set up a whole separate camps kind of thing here. I'm just pointing out that to my taste and critical eye, Hamburg's movies are much less predictable outside the general outline of these comedies.
For instance, the whole "gay" joke box of tricks all these comedies use for an easy laugh, Hamburg uses as well in I LOVE YOU MAN, but at least in some ways we haven't seen before (probably the best adjusted male character in the film is played by Andy Samberg playing Paul Rudd's character's gay brother, but playing him as straight as any character in any movie ever gets, so ordinary and so not stereotypical it elevates that subplot to a much more realistic and even in some ways enlightening level than these movies hardly ever achieve, and that's just one example).
Casting Jason Segal as the co-lead (to Paul Rudd) was smart too. His character is bigger than life, but also vulnerable and typical of the boy-men in these types of comedies, but Segal has such a unique presence on screen, he extends this type of character's usual obviousness into such a specific kind of realism of unpredictability and particularness he seems like a real person most of the time who just wandered onto the set.
Rudd has this attribute as well, but not in the Segal-uniquely-individual way, more in the Tom Hanks everyman way. Rudd's been a stalwart presence in these kinds of movies for years now, but when I first noticed him in the comedy CLUELESS back in the '90s, he came across as so authentic, such a fine actor, and yet so charmingly egoless, that I expected him to become one of his generation's major stars in serious movies.
But it's taken this long and this movie for him to become a true movie star, as it's his character that is at the heart of this movie, and with the help of Segal and the love interest, as they say, played by Rashida Jones—another unique screen presence that grounds the movie in a kind of realism these flicks usually don't have—Rudd and Hamburg, and the other collaborators that made this movie, pull it off.
It's not a run-out-and-see-immediately movie, so you can wait for it to go to DVD or get on cable. But if you run across it, don't ignore it. They say a good laugh every day helps the body heal and keep the immune system strong, well I LOVE YOU MAN worked for me like the flu shot is supposed to. I laughed out loud so much I was afraid I was disturbing the few other people in the tiny section of our local multiplex it was showing at. Not a bad recommendation for a comedy.