Really good watch, could watch again, and can recommend.
I forgot how well this movie holds up. Now, I'm not a fan of Vince Vaughn or Ben Stiller (most of the time), but, being objective, this is a pretty funny movie with a good plot to it. It has problems besides casting, but most of those are over in a blink and we're back to the movie.
This is a movie that leans on ridiculous humor, and everyone pretty much stays in their lane with quirks and motivations, and while the abuse humor of Justin Long pushes my boundaries of entertainment, Vaughn's lazy character work breaks it. I'd say it was a problem with the writing, but the delivery is sloppy even for someone playing a lazy character: the character is someone who knows what needs to get done and can't be bothered to do work, not someone who is too lazy to do what he can do.
Ben Stiller is over the top, but that's a combination of how the character is written and Stiller's delivery: I clearly don't like the character concept, but without him being an overly nice / secretly evil guy, I'm don't have a real suggestion there.
I'm sure you can make similar arguments for any given character, but the movie is actually so well produced, overall well written, and the performances are funny enough to distract from "problems" that if you just relax and watch this movie, you'll probably be laughing all the way up to "My Milkshake By's All the Boys to the Yard".