There was so much about this movie that I loved, that I'm giving it a pass for going off the rails a bit in the last act. Michael Shannon was amazing as Kim Fowley. The most remarkable thing about Fowley is that while Shannon seemed pretty extreme, the real guy is about ten times worse/better. Still, I don't know how anyone could have done more to catch Fowley's psychotic genius and abuse. The main actors were all strong, and many of the sequences have a real visceral impact.
Maybe I regret that some of the other characters were underused. Lita Ford is pretty much an extra, and who exactly is Alia Shawcat supposed to be? And the end goes on and on. I was itching to jump on screen and tell Kristen Stewart's Jett that she should stop being so self-conscious and do the singing herself, because it takes a really long time for her to figure that out. Those last ten minutes are a little like being the only sober person at a stoner party. The stoners still think they're interesting, but they stopped being interesting a while back.
I'm not going to quibble though. I had capital F fun for about three quarters of the picture, and sometimes that's all it takes.