I was apprehensive going into 
Kurt Cobain: Montage of Heck. Sanctioned by Cobain's estate, the documentary could be just one big love letter to Nirvana. And, in a way, it is. But in a more important way, it's not: It's tougher and more risk-taking than that. For 
Paste I 
reviewed the film, which will next be screening at South by Southwest.