Unlike Superbad or Knocked Up which are incredibly overrated and unfunny (yes, yes, I know they were huge hits and all but I just found they fell flat), Forgetting Sarah Marshall is note perfect.
The casting is superb especially Russell Brand who really steals the show. Throw in the bit parts from SNL's Bill Hader and Kirsten Wiig, 30 Rock's page Jack McBrayer, a Baldwin (William!) and a Barney Miller sighting in Steve Landesburg and we got an A&W level "2 for 4 Mama burgers" party.
Of the bit parts Paul Rudd stands out as a surfer dude without channeling a Spicoli. Thankfully, Apatow shoved the weakest link in Jonah Hill into a bit part in this movie because I'm sorry, the guy is should not be a leading actor as he is in other Apatow flicks.
Of the leads Mila Kunis is beyond perfect in the way she is the counterfoil to Kristen Bell. I would be remiss leaving out the man who brings new meaning to vampire puppet operas, Joel Segal.
The extras make it definitely worth picking up the DVDs. You get the usual director's/actors' commentary track, a gag reel, deleted scenes (some of which are gut-bustingly funny) as well as a line-o-rama that features the best lines from the movie. Also, there is an extended version of the movie as well as the actual one that was released in the theaters.