I'll bite.
DJ certainly isn't everyone's cup of tea, but his cult fame way predates Kurt Cobain and, even more so, the documentary.
He was a darling in the indie world for a long, long time prior to Nirvana. WFMU championed him seemingly from the get go, he was buddy-buddy with Sonic Youth, Yo La Tengo (who covered Speeding Motorcycle over twenty years ago), Jad Fair, etc.
I think he has some truly beautiful songs. But he is of course mentally ill, and because he produces so much stuff as a mechanism to deal with his illness, not everything is going to be brilliant all of the time or even most of the time.
I can certainly imagine him giving awaful performances, though.