Just to chime in.
Due to my distaste of 80s music in that vein, I didn't really enjoy the musical aspect of the film. Which, yeah, is sorta important. But the movie, dramatic bits that didn't involve the two leads were legitimately pretty fun. Alec Baldwin, Russel Brand, Paul Giamatti, Tom Cruise, all those bits, pretty damn entertaining.
It's a movie that is (mostly) the RIGHT kind of stupid. Not as bad as I was expecting.
The girlfriend loved it, but she's into musicals anyway.