Here’s what Kurt Loder said about it:

But seeing the picture on a big screen was, it must be said, a revelation. Apart from the hot stuff of legend—the desultory smack-shooting, the raw groupie-banging—the movie’s real subject is the exhaustion and monotony of life on the road, and the exhilaration of those few hours onstage every night that make it all, or almost, worthwhile. The film’s technical cruddiness might almost be a formal strategy—the drugged-out rhythms draw us in and slowly work us over.

via Reason.com.