If you don't have plans to see this movie, you can check the spoilers here and then come back.
I was a bit nervous about this movie because I thought Russell Brand's Aldous Snow character in "Forgetting Sarah Marshall" was hysterical, but in large part because he was a fairly one note background player, and was unsure he (Brand or Snow) had the chops and depth to sustain a feature. Well, it turns out not only does a more layered and nuanced Aldous Snow make for a great lead character, but Russell Brand has more than enough facets to his own talents to make it work; the stuff that was supposed to be funny almost always was with Brand's performance, but seriously, some of his more down-to-earth and heartfelt scenes were probably my favorite bits. I could honestly watch two or three more movies with the Snow character as an anchor because of how fully Brand inhabits and seems to enjoy playing him, tossing off one-liners and monologues effortlessly, but also really taking the time to give his work a distinct physical personality. However, Brand isn't flying solo by any means, as this is one of the best things I've seen Jonah Hill do also. It was a nice change of pace to see him playing the ostensible straight man as Aaron Green as opposed to the goofball or sidekick, and he's really good at it; really earnest and able to make you care about what he's going through. This was also one of the better physical comedy performances I've seen Hill in as Nicholas Stoller really came up with some insane sequences that he excelled in. Quite a strong supporting cast as well, in particular P. Diddy who stole pretty much every scene he was in by virtue of how confidently and over-the-top aggressive he was as Green's boss at Snow's record label. Rose Byrne has the tough task of having to match Brand in quirk and zaniness sharing scenes as his ex, but she pulls it off with gusto. And it was neat to see Elisabeth Moss as Aaron's cute girlfriend if only because I've never seen her in anything other than Mad Men. If this film had any weaknesses it was only that with such a great group of players to showcase, it did waste a fair bit of time with generic party and travel sequences that weren't that funny at the expense of the really good stuff; ultimately though, the good stuff was more than good enough to make this an instant new favorite for me.