Saw Walk Hard yesterday (orange wednesdays baby!), and I was right before when I wrote all this in anticipation: 

"Walk Hard is to musician biopics (Ray, and Walk The Line more specifically) what Anchorman was to TV News. At least i think it is. I haven't seen it yet but the trailer sold me before it had even finished. If you can't laugh at the prospect of Paul "It's called Sex Panther" Rudd (who was great in Knocked Up last year) as John Lennon then I can't help you. The best bit is that he's not even in the main cast, so the quality of the humour in the main story's gotta be high. 

If you're worried about music being belittled in Walk Hard then all i can say is - Jack White as Elvis"

As a whole, the film has a stronger sense of genre than Anchorman - The Legend of Ron Burgundy, because its is a spoof of the musical biopic genre. It is mostly a parody of Walk the Line, the Johnny Cash biopic starring Joaquin Phoenix, so you'll get more laughs from Walk Hard if you see that first. Other than that, Walk Hard draws on the stories of any number of legends of music - Bob Dylan being a good example. The film features cameos from almost everyone who's ever been funny in a Judd Apatow film - Paul Rudd as John Lennon, Jack Black as Paul McCartney, Jason Schwartzman as Ringo Starr and Justin Long as George Harrison. They don't have much screen time, but are very funny together as The Beatles, especially because they're Liverpudlian accents are all over the place.  Jack White is excellent as Elvis, and Frankie 'Malcolm from Malcom in the Middle' Muniz even makes an appearance.

I haven't laughed so hard since I saw Knocked Up and Superbad - also from Apatow. He is truly a comedy genius.

Much kudos to John C. Reilly as the eponymous singer who grows from a small town blues guitarist aged 6, to a music phenenom with scores of offspring, who recounts the story of his life and music. 

The songs are Spinal Tap-esque in places and always sung pitch perfect by Cox and his band. Check out the official site (especially the soundboard) for a taste of Dewey Cox.

You'll never machete-fight in the same way again.