It's tough to create a new and interesting plot for a rock and roll biopic because there's basically one trajectory they all take:

"Band is young and naive, they get popular, take a lot of drugs and are torn apart by their egos".

If the story is that familiar, it basically comes down to the script and the performances to make it interesting. Also it helps if the characters are hot girls strutting around in tight clothes.

I didn't find the script of "The Runaways" to be anything special, but there are some pretty good performances in the movie.  

Dakota Fanning was pretty convincing at Cherie Currie, the baby-doll singer of the first all-girl hard rock band.  Michael Shannon creeped me out as Kim Fowley, the band's svengali.  

And somehow, without really saying much, Kristen Stewart seemed to embody the role of Joan Jett--her drive and passion to create music.  Cherie Currie was recruited into the band by Fowley, but Stewart really made me believe that Joan Jett was going to succeed no matter what, because music is her life and her obsession.

The songs of The Runaways don't stand out too much to me, but the film had a really stylish and sensual look, very much in tune with the concept of the band--sexy young girls playing ballsy rock-and-roll music.