I really enjoyed Forgetting Sarah Marshall, from which this flick is a spin-off, and I enjoy Jonah Hill's comedic performances ... I'm not keen on Russell Brand though.
Still, I was able to separate him from Aldous Snow enough for my own liking with FSM, and was similarly able with Get Him To The Greek. So the major hurdle, which had left me not so keen on seeing this flick, was overcome.
Annoyingly though, the film takes seemingly ages to get going. The opening portion is just full of exposition that isn't written or performed with any sense of comedy, so the cinema was pretty darn laugh-free, so we all had to wait until the main thrust of the movie got underway - Jonah Hill's record company gopher escorting Brand's libidinous rocker from London to the Greek Theatre in L.A. - before the laughs came, and fortunately they came pretty regularly from this point on.
The movie makes no real observations about rock and roll, celebrity life, or much else in-between ... it's just out for a good time like the Aldous Snow. The movie is a shot of Absinthe rather than a considered Ale. There's not an awful lot to it, but it's fun while it lasts (well, after that deathly dull portion before we arrive in London that is).